Tenth-grader Brian Hollenbeck always gets two questions when he recruits other students to his school.

“How do you live without girls?” they ask, and “How do you tie a tie?”

Brian, 15, attends the Young Men’s Preparatory Academy, a Miami-Dade all-boys public school. Students wear ties and blazers and the goal is to hone boys into young men, ready for college. It is one of a growing number of single-gender public schools in South Florida.

This year, the Broward school district started a pilot program, offering all-boys and all-girls classes as an option at six schools, which still provide co-ed classes as well. Though experts debate the merits of single-gender classes — some argue there is no clear evidence they succeed — administrators and teachers here say they’ve seen them dramatically improve the performance of some students.

“We’re trying to really give our young men leadership,” said Young Men’s Principal Leonard Ruan. By separating boys from girls, the students have fewer distractions and can focus on their academics and leadership skills, he said.

Ruan’s school started with high school grades. But it is adding middle school grades, starting with sixth this year, in the hopes of replicating the success of its sister school. The Young Women’s Preparatory Academy in Little Havana, which serves grades 6-12, has 300 on the waiting list and was ranked No. 2 in Florida and No. 26 in the nation by U.S. News & World Report.

Supporters of the single-gender model say it takes away distractions by allowing boys and girls to focus on academics and building their confidence. But there are plenty of critics.

In West Virginia, the American Civil Liberties Union recently won the first battle in its lawsuit against a public single-gender school, claiming discrimination. A judge there issued a temporary injunction because the class assignments were mandatory — not voluntary, as they are in South Florida.

There are also concerns that single-gender schools can reinforce gender stereotypes, spur discrimination or fail to prepare kids for the real world.

Elena Silva, senior associate with the Carnegie Foundation in Washington, D.C., said none of the research is very powerful, one way or another.

“It’s not to say that it can’t work and it doesn’t work, but there isn’t very strong research … that single-sex education is any better than coeducation in terms of student outcomes,” she said.

Public schools’ policies should rely on sound research, she said. “If it’s really so good for kids, then all kids should be doing it,” Silva said. “There’s a reason we’re not. The private elite schools that are single-gender, they don’t function so well because they’re single-gender. They function so well because they’re private elite schools.”

In South Florida, there are four single-gender Catholic schools, stemming largely from tradition.

At Our Lady of Lourdes Academy, Principal Sister Kathryn Donze said the success of a school relies on more than being all girls or all boys. It’s about mentoring students, strong faculty and instilling a lifelong work ethic. But with only girls, Donze said girls take on more leadership roles.