Families lined up outside Brooklyn Technical High School in October to enter the city's annual high school fair. Concerned that there are not enough high-quality choices, many charter school networks are opening high schools of their own.

If all goes according to Success Academy Charter Schools’ plan, this year’s seventh-graders at the network’s first school won’t have to hunt for a high school.

The network is asking the state for permission to expand the school to ninth grade in 2014, the year that its first cohort will hit high school. SUNY’s Charter Schools Institute, which authorizes the school, is holding a hearing about the proposal on Tuesday and will decide whether to approve it as early as January.

The proposal does not represent a commitment to add high school grades to all of the network’s schools, according to a spokeswoman. But it does reflect the charter sector’s growing realization that ending after eighth grade would mean sending thousands of students a year into a high school admissions process that can be difficult to navigate and can result in assignment to a low-performing school.

In the past, many high-performing charter schools have sought to place their graduates in selective high schools or get them scholarships to private schools in the city and beyond. But with more students graduating from charter middle schools each year, there are not enough seats to go around, and the schools are creating their own.

The KIPP network added an elementary school in 2009 and a high school in 2010, while Democracy Prep has run a high school since its first students graduated from eighth grade and added an elementary school last year when it took over a struggling elementary school, Harlem Day Charter School. Since 2009, eighth-graders graduating from Uncommon Schools or Achievement First schools have been able to continue on in consolidated high schools operated by the networks.

If approved, Success would be the largest of the city’s charter school networks to craft an uninterrupted kindergarten-to-graduation pathway for their students. When the 14 schools currently in operation in the Success Network have fully scaled up, they could have more than 2,000 eighth-graders each year — and the network is still expanding, with six schools proposed to open in 2013.

About 80,000 students apply to city high schools each year, with about 10 percent getting shut out of all of the schools to which they apply.

“While we might be able to place our first two [smaller] classes in other high schools, our classes quickly become too big to ensure we can place every child in a high quality program,” said Kerri Lyon, a Success spokeswoman. “Our goal has always been college graduation and we think this will put our students on the right track towards fulfilling that mission.”

Some charter school networks are sticking to a smaller niche, despite having some of the same concerns. At a panel discussion last week about diverse schools, the CEO of the Explore Schools network, Morty Ballen, said he was committed to focusing on elementary and middle school grades. But he said a downside is that his students might have to leave their neighborhoods and their communities if they want to attend a high-quality high school.

“Our approach is K to 8 and we’re not going to tell kids, ‘Don’t go to Trinity [an elite private school], stay here and go to the high school around the corner,'” Ballen said. “Not when the high school is crappy — and there are a lot of crappy high schools.”