Mount Vernon Community School got a new principal this year, and teachers were skeptical. Peter Balas is the third in five years to lead the Alexandria elementary school.

“When we found out we were getting a new principal, everyone was like, ‘Again?’ ” said Holly Rocchetti, a fifth-grade teacher.

Balas, 33, was an administrator at T.C. Williams High School for four years and a teacher for six, but he had no elementary experience. Teachers asked him what he knew about educating younger kids.

But Balas was there for a reason. Mount Vernon has below-average test scores overall and a growing achievement gap between its white and Latino students. The disparity became so glaring that last year Superintendent Morton Sherman marked it for “transformation,” or a top-to-bottom makeover. Balas had worked on a similar metamorphosis as an executive associate principal at T.C. Williams, where the passing rate on English tests rose to 95 percent in 2011, from 84 percent two years prior. Now, Sherman hopes Balas can help replicate those gains at Mount Vernon.

“A successful transformation isn’t just about new programs, it’s about a spirit,” Sherman said. “Peter Balas has that spirit.”

Classes began Aug. 1 at Mount Vernon, one of the few schools in the area that opens at such an early date. (Because of the school’s modified calendar, the school’s summer vacation is shorter but there are more short breaks throughout the year.) Balas strode through the halls one day this week, patting heads and saying hello. He worked the crowd in the cafeteria and reminded students that the most voracious readers would get to dunk him in a tank at the summer reading party at the end of the week.

“It’s nice to have my kids come home laughing about the funny things he’s said,” said Lisa Guernsey Krupicka, a mother of two at the school. “Our previous principal was known for her whistle.”

Academically, Mount Vernon faces challenges familiar to many public schools in economically diverse areas. A third of the 713 students are non-Hispanic white, and 57 percent are Hispanic. About 40 percent of the students are English-language learners. Sixty percent come from families poor enough to qualify for meal subsidies.

“Some kids get to kindergarten not knowing that letters make sounds,” said Maria Fletcher, a third-grade teacher.

While the school’s white students perform above the city average, its Latino students are far behind. In third-grade math, for example, the gap in passing rates widened to 24 percentage points in 2011 from 12 points in 2007.

“The teachers were doing everything they could do as professionals and not seeing the results,” Balas said. “They felt beat up.”

He wasted no time in making changes.

Among the biggest challenges was employee morale. Twenty teachers left Mount Vernon within the past year, out of 50 total, citing a combination of personal reasons and frustration with the school’s trajectory. There had also been turnover at the top. Tina Radomsky, Balas’s predecessor, resigned in the spring after less than two years as principal. The previous principal, Scott Coleman, served from 2007 to 2010.

“It was hard, because once you get used to one person, we had to get used to a whole new agenda,” Fletcher said. “There was a lot of struggling to figure out what was expected of us from the leadership.”

Teachers were stressed by the demands of day-to-day lesson planning combined with striving — and sometimes failing — to meet test-score benchmarks.

This school year, to help ease the pressure and foster subject-area expertise, instructors will teach only a few subjects each — some, math and science; others, language arts and social studies — and will rotate classes in the afternoon.

On Monday, Fletcher passed around a piece of folded paper, telling students to use their senses to describe its physical properties.

“What sense do you use to tell if it’s white?” she asked.

“Your sense of humor!” someone squealed.

She’ll repeat this science lesson in the afternoon for the second set of students.

“This will give us a chance to focus on two areas and really plan those well,” Fletcher said.

To instill pride, Balas introduced school colors (blue and red) and a mascot — a lion sporting a conductor’s cap, a nod to an old train car on the school grounds.

“I like that it’s a lion,” said Henry Arevalo, 11, a fifth-grader. “It’s a cool animal.”

Measurement and enrichment have taken center stage.

Under Balas, teachers will take a course on best practices in instructional styles. For example, every 10 minutes of teacher talk should be followed by two minutes for students to reflect, he said.

All students are being tested to determine their reading level, and they’ll be grouped by ability for daily, 90-minute structured reading lessons.

Balas also created a community room for families to drop in, use computers and meet with instructors. He doesn’t speak Spanish, so he bought Rosetta Stone, the language-learning software, and plans to be conversant by June.

School was off to a smoother start than in recent years, according to several staff members, and teachers said they feel respected and heard.

“Mr. Balas is very approachable,” said Lisa Bryson, who heads Mount Vernon’s reading program. She said he’s willing to admit shortcomings. “If he doesn’t know something, he’ll say, ‘Hey, I’m not sure.’ ”

Changes in leadership can be disruptive for any school, but a revolving door of principals can create a “trust gap,” said Mark Terry, president of the National Association of Elementary School Principals.

A new principal should listen to staff suggestions and assure them that he’s there to stay, Terry said, much as Balas has tried to do.

“Those teachers who are on board will rally up behind you,” Terry said. “But then you’ve got to prove yourself.”