Javon Roach, left, a third-grader at Kimball Elementary, cocks back to throw during an after school practice at the Washington Nationals Youth Baseball Academy in Southeast. (Bill O'Leary/Washington Post)

When baseball returned to Washington in 2005, it was with the understanding that the Nationals and the District would work together to build an academy that would help promote baseball among young people in the inner city, where interest and participation in the sport has been declining for years. Rough details were included in the lease between the District and the franchise for Nationals Park. But for a time it was unclear when the dream for the nine-acre plot of land in Fort Dupont Park in Southeast would become a reality.

But after years of fundraising, preparation and bureaucratic and construction delays, the Washington Nationals Youth Baseball Academy is finally open. The ambitious, gleaming building that cost nearly $18 million welcomed its first class of children three weeks ago and will be officially unveiled Saturday at a ribbon-cutting ceremony before the Nationals’ exhibition game against the Detroit Tigers.

Third- and fourth-graders fill the 18,000-square-foot, two-floor facility after school, learning to play baseball and softball on its three artificial turf fields and doing their homework and extra classwork under the watchful eyes of mentors in the seven upstairs classrooms.

“The kids today are now children of people that didn’t grow up with baseball in Washington,” said Marla Lerner Tanenbaum, a principal owner of the Nationals and chair of the team’s charitable wing, the Washington Nationals Dream Foundation, who led the construction of the academy. “The culture of baseball in Washington needs to be revived. The culture of inner city baseball, especially in African American communities, needs a jolt.”

In the major leagues, African Americans accounted for just 8.5 percent of the rosters on opening day last season, nearly half the number 20 years earlier. In Washington, baseball lost its foothold in all but the most affluent neighborhoods. So city officials such as District Mayor Vincent C. Gray (D) pushed for the youth baseball academy in Southeast as a councilman during stadium negotiations with Major League Baseball.

The Post Sports Live crew helps Matt Williams fill out the Nationals starting rotation by offering suggestions of who to name as the fifth starter. (Post Sports Live/The Washington Post)

The biggest hurdle: securing the land from the National Park Service, which finally gave its permission in 2010, Tanenbaum said. The Nationals began construction a year later, and after some delays, the inaugural class moved into the completed facility March 4.

The city donated $10.2 million of the $17.7 million cost of construction, according to Tanenbaum. She said the team and Dream Foundation combined to give $3 million, in addition to the charity wing’s commitment of $250,000 a year for operating costs for 10 years. Major League Baseball donated $1 million, and several companies also made contributions.

The academy has a college-sized stadium that seats 500 people with two adjacent smaller fields for softball or Little League. There is a 4,800-square foot indoor fitness area with a padded turf floor and two collapsible batting cages. But because officials didn’t want to focus solely on sports, the main building also has classrooms, a teaching kitchen and a curriculum to serve the community’s education needs.

“We’re working in a population where baseball hasn’t been a popular sport for some time,” said academy executive director Tal Alter, 38, a Bethesda native and Landon graduate who played baseball at Haverford College and worked at several nonprofits before being hired by the Nationals last April. “We don’t have any illusion, nor do I really think about development of baseball players; we’re not trying to create baseball players. But we are trying to use the values of baseball to create a positive culture, and all these other things can happen.”

The academy partnered with three elementary schools in Ward 7 and 8 to help identify its students. Three times a week, starting at 3:45 p.m. during the school year, they spend four hours at the academy after class: one hour for mandated homework time, an hour of baseball instruction and activities, then dinner and another hour of either supplemental reading, math and science or cooking classes, both done with the help of local nonprofits.

Former baseball and softball players serve as part-time coaches and teachers and are supplemented by volunteer college-aged and adult mentors. Students from charter school Cesar Chavez High also provide volunteer classroom help.

“It’s fun because, for example, if I can’t do my homework they help me,” said Jelani Taylor-Thomas, a fourth-grader at Anne Beers Elementary in Southeast. “Or if I can’t throw, they help me.”

To reach capacity, the academy will add a class of about 40 third-graders each summer until it fills each level through eighth grade. During the summer, the children will be at the academy from 8 a.m. to 4:30 p.m. five times a week. In the future, Alter said the academy hopes to add programs for K-2 and high schoolers. And it may create leagues and tournaments for the students to play in games.

Everything, even learning, is tied to baseball to make it fun. During recent bad weather, children watched the movie “42” and learned about Jackie Robinson. They read stories about former Negro League great Josh Gibson, who played in Washington for the Homestead Grays. Math is geared around baseball-themed questions and statistics. As the kids grow, physics, engineering and biology activities can be tied to the sport.

“You can infuse baseball in just about everything,” Alter said.

On Thursdays, the students learn about healthy eating in the classroom kitchen, prepare and cook meals and clean up. Recently, they made oatmeal flaxseed chocolate chip cookies with avocados as a substitute for butter. Alter plans to build a vegetable and fruit garden at the complex, too.

Part of the academy’s mission is also to involve the rest of the community. An area collegiate summer baseball team, the D.C. Grays, will use the academy as its home field this year. Two local high schools, private Gonzaga College High and public Anacostia High, already use the fields and indoor batting cages for practices and games. Players from both schools help with the children’s baseball instruction. Nationals players and coaches may also help out during the season. General Manager Mike Rizzo and shortstop Ian Desmond sit on the academy’s advisory board.

“It’s going to be a process of building that culture of baseball,” Alter said. “I’m perfectly willing to admit that people have every right to be skeptical. There hasn’t been a lot done — and I’m not saying by the Nationals — just generally speaking for neighborhoods east of the river. The problems that people face over here are very real. It will take some time for people to see that we’re not just building this facility for outsiders to come in and use. This really is a resource for the local community. We want people to be here and take part in what we have going on but also to learn and be a part of learning about the game.”