Inside a prefabricated beige building hard by the freight tracks, John Danner thinks he has solved one of the nation’s most vexing problems.

This is Rocketship Discovery Prep, one of five charter elementary schools founded by Danner that are bridging the achievement gap — the staggering difference in academic performance between poor and privileged children.

The gap — which has persisted for decades despite heavy investments of time, energy and money — can cement the path a young life takes. Poor children are likely to enter school already behind, never catch up and then drop out, joining an underclass that threatens the country’s economic future.

Policymakers, foundations and business leaders are ravenous for schools that can educate all children, regardless of income. And they don’t want just a handful of successes. They want a big idea, on a grand scale.

Danner, a boyish 45-year-old Silicon Valley entrepreneur and onetime public school teacher, believes he has the answer.

On standardized tests, Rocketship students — overwhelmingly poor, Latino and Spanish-speaking — have outscored the county and state average. In some cases, the “Rocketeers” have performed as well as students in nearby Palo Alto public schools, where Stanford University professors send their children.

Danner wants to take his model and expand it into the nation’s largest chain of charter schools, reaching 50 cities by 2020.

Rocketship’s scores, combined with an unusual educational and financial model, have made it the darling of the school reform movement. Cities across the country, including in the District and New York, are clamoring for Rocketship to set up shop. The Obama administration has invested $2 million to speed its growth.

But some wonder if five-year-old Rocketship is producing miracles or mirages. Will a model that succeeds in San Jose also flourish in Nashville? Can a strategy that works for a handful of schools be expanded across the country? And can the achievement gap be eliminated?

Answers may be found next year, when Rocketship ventures outside of northern California to open the first of eight schools in Milwaukee.

To some, Rocketship’s rise represents another step toward a gradual abandonment of traditional public schools, placing more children — and public dollars — into the hands of private operators.

Stephen McMahon, president of the San Jose teachers union, worries that a dual system is developing: One filled with charters that attract motivated families and another of traditional public schools populated with reluctant learners.

“It’s almost harkening back to the days of segregation,” McMahon said.

Charter schools, which are publicly financed but privately run, must accept any student, the same as a traditional public school. But families have to seek out a charter school, apply and, if demand exceeds capacity, enter a lottery for a seat. The charter may be located across the community, requiring families to transport their children back and forth each day.

“I don’t want every committed family at a charter school and those who are struggling at traditional schools,” McMahon said.

McMahon stressed that he is neither anti-charter school or critical of Rocketship. In fact, he said, he admires some of Rocketship’s innovations.

What sets Rocketship apart from other successful charters is a financial model that allows it to operate on government payments without continual infusions of cash from private donors. Many successful charter schools require additional funds to cover the costs of a longer school day, intensive tutoring and other expenses.

But after initial start-up costs, Rocketship schools are largely self-sufficient because they use technology to re-engineer the classroom.

For two hours each day, students are taught by computers designed to meet children at their particular level and drill them in rote skills like addition or subtraction. They spend the rest of the day in more typical classrooms with teachers, tackling more complex work like critical thinking.

Computers shave 25 percent from Rocketship’s labor costs — savings used to extend the school day to eight hours, pay higher salaries to its nonunion teachers and to construct its own school facilities, among other things. One Rocketship school is a replica of the next — everything is identical, down to the paint scheme: forest green and beige with purple accents.

Cities vie for schools

Last year, D.C. Schools Chancellor Kaya Henderson shook hands on a deal to bring eight Rocketship schools to the District. In January, New York Mayor Michael Bloomberg announced Rocketship was en route to his city.

Both announcements turned out to be premature: It can take years for Rocketship to identify and train school leaders, and neither Henderson nor Bloomberg has legal authority to approve a charter school. But the high-profile statements only amplified the buzz.

All the attention nearly obscures the fact that Rocketship runs only five schools — two of which, including Discovery Prep, just completed their first year and lack state test results. But internal tests given five times a year showed that by May the new schools were on track to perform as well as the others, Rocketship officials said.

That’s significant for a school population where the percentage of children eligible for free and reduced lunch, an indicator of poverty, ranges as high as 92 percent and the portion learning English can reach 80 percent.

“There aren’t a lot of proven solutions out there, and there’s a tendency for people to glom onto something that could have a lot of impact,” said Jim Ford, an education consultant who once worked for one of Rocketship’s earliest funders.

In addition to Milwaukee, Rocketship has won approval to open schools in Indianapolis, New Orleans and Nashville. And it has permission to open 20 additional schools around San Jose, as well as one in San Francisco.

Despite the courtship of Rocketship by some cities, it hasn’t all been flowers and candlelight.

Approval for the San Francisco school came from the state after the city’s school board said no. City officials criticized the commercial software Rocketship uses and its English-only approach to teaching Spanish-speaking children, among other things. In Oakland, Calif., the board of education also spurned Rocketship, saying it lacked experience educating African American children. A bid to open a Rocketship in East Palo Alto met a similar fate.

Across the country, charter schools enroll fewer children with learning disabilities than traditional public schools, according to a federal study released last month.

And that’s true of Rocketship, where 6 percent of the students are classified as having learning disabilities — about half the rate found in the surrounding traditional public schools.

Children with disabilities are more challenging and expensive to educate, and they often do not perform as well on standardized tests.

Some of Rocketship’s special education students have progressed enough to be reclassified as regular students, said Melissa McGonegle, Rocketship’s regional vice president of Bay Area schools. In addition, more than half of its students are younger than the typical age — second grade — when disabilities are detected, she said.

Three of the five Rocketship schools are still building out, adding a grade a year until they reach fifth grade. Of the 2,400 students who attended Rocketship schools in May, roughly 1,800 are in kindergarten through second grade.

McMahon, the union president, has challenged Rocketship to take over a failing public school in San Jose to test whether it can educate all children. “Then we can answer the question — is it the instructional model or is it the students?” he said.

Rocketship is cool to the idea. Autonomy — freedom from the bureaucracy and union rules that come along with traditional schools — is key, Danner said.

The chain operates only elementary schools; Danner said he is dedicated to closing the achievement gap in the early grades.

Rocketship relies heavily on Teach for America, the nonprofit organization that gives new college graduates five weeks of training before placing them in teaching jobs. Three out of every four Rocketship teachers are either in the program or recent alumni. Danner said he is using Teach for America as his human resources department because it vets candidates well.

Critics, including several school superintendents in the San Francisco Bay Area, say Rocketship uses a low-cost “industrial” model that depends on inexperienced teachers and computers. And they question whether a national chain would interfere with local control over education.

Sobered by its early political fights in California, Rocketship now has three requirements before it considers moving into a new city: authority to create at least eight schools, $3.5 million commitment from local private donors to pay start-up costs and school leaders who have worked for Rocketship for at least two years, so that they are immersed in its culture.

In the ‘Learning Lab’

There is scant research about the impact of computer learning on students, particularly those in primary grades.

At Rocketship, it’s hard to say whether strong test scores are the result of the computers, teachers, school culture or some combination.

In each Rocketship school, children file into a “Learning Lab” every day, where they sit at computer carrels that line the perimeter of the room.

In the center of the room, tutors work in small groups with children in need of more intense help. In a traditional public school, students would be pulled out of class for that kind of extra help, losing valuable classroom time that can often push them even further behind.

At the computers, each child logs onto a program that continually adapts, spending more time on tasks that the student finds difficult, advancing when the student demonstrates mastery.

One morning this spring at Discovery Prep, Ebony-Princess Cutts thumbed through a stack of printouts as first graders clicked away at their computer stations. Cutts, a Learning Lab aide who is not a certified teacher, earns about $14 an hour with benefits.

“This tells me that he’s struggling,” she said, referring to a chubby boy sitting at the end of a row of computers, his small ears swallowed by big blue headphones. “I wouldn’t ordinarily notice that because he’s quiet and he looks like he’s engaged.”

Later, kindergarteners filed into the Learning Lab and slid into their seats. Of nine students, three faced their computers while the others played with their headphones, poked each other and glanced everywhere but the monitors.

Danner acknowledges that the youngest students have trouble concentrating, although he said internal data show the kindergartners and first graders complete as many computer lessons as older children.

As the quality of software improves, Danner thinks “Rocketeers” could spend as much as 50 percent of the school day with computers.

A handful of other charter school operators are experimenting with blended learning, including two Los Angeles elementary schools that are part of the Knowledge Is Power Program or KIPP.

The KIPP schools were forced to use computers after state budget cuts resulted in teacher layoffs. The experiment is going well, but KIPP does not plan to expand it, said Mike Feinberg, a co-founder of the KIPP network. “The recipe is great teaching and more of it,” he said.

Offloading rote work to computers

As far as Juan Carlos Martinez is concerned, the Rocketship computers have delivered great teaching.

Martinez has three children in third grade. His daughter, Vivian, was hopelessly confused by basic math. His sons, both autistic, struggled with everything, and one was in a special-education class that didn’t seem to help.

Martinez, who remodels houses, and his wife, a nurse’s assistant, couldn’t afford tutoring. Uncertain what to do, they pulled the children from the neighborhood elementary school and enrolled them this past November in Discovery Prep at a friend’s urging.

Rocketship tested the children and found they were performing at the first-grade level, which shocked Martinez.

After their first week at Rocketship, the children woke up early on Saturday morning to do their homework unprompted. The boys made progress. And Vivian had a math breakthrough. “She said, ‘Dad, I finally get it,’ ” Martinez said. “I asked how did your teacher show you?’ She said it wasn’t the teacher. It was the penguin.”

An animated penguin is featured in the math software used by Rocketship.

Computers cannot replace good teachers, Danner said. But rote tasks — math drills, for example — can be offloaded to computers, freeing teachers to focus on more creative work, he said.

Computers cut roughly $500,000 annually from Rocketship’s labor costs for each school, which has an average enrollment of about 500. The savings means Rocketship can finance its own new school buildings — a luxury in the charter world, where facilities pose the greatest obstacle.

It also uses the windfall to pay for staff training and higher salaries for its teachers, who earn about 10 percent more than those in surrounding public schools. Teachers can earn another 10 percent in bonuses if students meet performance goals.

Mindful of teacher burnout that plagues high-poverty charter schools, Rocketship provides a month of training before school starts and professional development through the year. Rocketship is also quick to promote teachers, who can run a school after just a couple of years in the classroom.

Even so, about 25 percent of the teachers do not return each year, which is in line with the national attrition rate for young teachers in high-poverty schools.

Devon Conley, 32, a Yale-educated kindergarten teacher at Discovery Prep, arrives at school about 7 a.m., stays until 5 p.m. and works a couple of hours more at night from home.

Like most of her colleagues, Conley loves her job and speaks of the “mission” with great passion. Still, she said, “this is not for the faint of heart.”

Finding a better way

Danner grew up alongside the technology industry in Silicon Valley. From his first computer at 12 — an Apple II — he was smitten. After earning an electrical engineering degree from Stanford, Danner worked for a series of tech start-ups before creating his own, NetGravity, the first company to write code that placed ads on Internet search engines and other sites.

After Danner sold his company and became a multimillionaire, the Jesuits who ran his Catholic high school sought a donation. Danner opted instead to help them create a private middle school for at-risk boys in San Jose. “I wasn’t really interested in just giving money,” Danner said. “I wanted to get involved.”

He acted as the chief operations officer, securing and fixing up the school building, hiring the principal, crafting the budget.

When his wife got a job teaching law at Vanderbilt University, they moved to Nashville. Danner earned a master’s degree in education and taught for three years in the city’s public schools.

Faced with a classroom of second-graders at varying levels, Danner devised plans for each student. But he was convinced there must be a better way to teach, one that used technology designed to make teaching more efficient.

Upon his return to California in 2006, Rocketship was born.

Rocketship, which is a nonprofit organization, takes 15 percent from the public funding it gets for each student as a management fee and uses it for accounting, payroll and building maintenance, as well as curriculum and professional development. Danner earns $150,000 a year.

“Very few people understand both K-12 and tech,” said Reed Hastings, the chief executive of Netflix and an early donor who now co-chairs Rocketship’s national strategy board. “John is one of the crossovers.”

Data is king

Like other high-performing charter schools, Rocketship emphasizes discipline, responsibility and achievement.

Each morning at Discovery Prep starts with a ritual called the “Rocketship Launch.” One day this past spring, several hundred children gathered on the asphalt lot outside the school, dancing with their young teachers as The Jacksons’ “Blame It On the Boogie” pumped from a boom box.

“Rocketeers, are you ready to focus?” shouted one teacher, who was rewarded with a high-pitched chorus of “Yes!”

The children streamed into the school, passing under Yale, Cornell and other collegiate banners. There are frequent and deliberate references to college throughout this elementary school, located in a neighborhood where students are more likely to drop out of school than attend a university.

The walls inside Discovery Prep are plastered with messages like “Work Hard, Talk Smart, Every Minute, Every Day” and handmade posters measuring student progress.

Rocketship focuses exclusively on reading and math; it encourages classroom teachers to try to incorporate science, the arts and other subjects into math and literacy lessons.

A great deal of preparation is focused on the state’s standardized tests taken in early May, the all-important metric by which schools — and Rocketship’s success — are judged. Some say Rocketship uses a “drill and kill” approach, where students become adept test takers but perhaps not critical thinkers.

“I feel conflicted about it,” said Dan Valedespino, a 24-year-old math teacher. “I try to wed the conceptual to the test taking. But that’s the game that these kids are in. Those colleges are going to know their scores.”

Data is king at Rocketship — in addition to two state tests, Rocketship students take eight internal tests during the school year. Every six weeks, teachers and administrators close school for a day to analyze test results.

Rocketship also goes to great lengths to involve parents, requiring them to pledge to read to their child every night, check homework daily, attend monthly meetings and volunteer 30 hours each year, among other things.

The bond between the school and families is further cemented by home visits.

“One teacher played ‘Chopsticks’ on our piano,” said Patrice Lindo, whose three daughters attend Rocketship Si Se Puede in San Jose. “I’ve never seen anything like it. They give their cellphone numbers, and the kids can call them until 9 or 10 p.m.”

Danner sees parents as an untapped force that could transform education politics. Rocketship has bused hundreds of parents to pivotal public meetings. It encourages parents to help elect politicians friendly to charter schools. In 2010, Rocketship helped parents create a political action committee that worked to elect three school board members in San Jose.

High stakes, potential pitfalls

Twenty years after the first charter school opened in this country, momentum is shifting fast from the early “Mom and Pop” stand-alone schools toward larger operations. But there are risks to growth.

As a charter organization expands, it can begin to resemble the school district it was formed in reaction against, said Robin Lake, director of the Center on Reinventing Public Education at the University of Washington. And the bigger it gets, the harder it is to maintain quality, she said.

“They’ll never be big enough to solve the problem, and the minute they do get big enough, they’ll be the problem,” said McMahon, the San Jose union president.

Currently, KIPP is the largest nonprofit charter network, with 109 schools in a franchise arrangement.

“We feel a heightened sense of urgency . . .,” Feinberg said. “But if we aggressively try to address all of it tomorrow, we’re going to fail. We have to have a maturity of patience.”

As Rocketship expands into new cities, if results fall short, the aura that surrounds it could quickly reverse, said Ford, the consultant.

Already, Rocketship has experienced some growth pains. Standardized test scores for its oldest schools dipped slightly last year and the chain has been slowing its expansion schedule in California because it has had trouble finding enough principals.

Danner is aware of the high stakes and pitfalls ahead. He worries about the downside of fast growth, that Rocketship will lose control of quality and morph into a bloated organization.

But he says he is compelled to push forward.

“We know we can do a smaller set of schools even better than a large number,” he said. “But we owe it to communities to continually open more schools.”