Students board a school bus at 6:45 a.m. in the Kensington area of Montgomery County in this November 2012 photo. (Susan Biddle/The Washington Post)

Efforts to ease sleep deprivation among teenagers in the Washington region have expanded, with at least four suburban school districts now examining whether the first bells of the high school day ring too early in the morning.

School leaders in Anne Arundel and Howard counties have announced in recent weeks that they are looking into later high school start times, just months after Montgomery and Fairfax counties decided to pursue the issue.

High school classes begin between 7:17 a.m. and 7:25 a.m. in the four school systems, with most students heading to bus stops in the 6 o’clock hour. Many parents and others seeking a change want to reset opening bells to sometime after 8 a.m.

“I think there’s a lot of momentum right now,” said Judith Owens, director of sleep medicine at Children’s National Medical Center.

The growing interest comes as advocates work to gain support for the idea nationally. On Friday, several are scheduled to give a presentation at the annual conference of the National Association of Secondary School Principals, being held at National Harbor.

Experts say that the biological clock of teenagers is geared for later bedtimes and later wake-ups and that a lack of sleep is linked to problems including depression, absenteeism and low academic performance.

Changes to the start times can be complex and expensive: Many school systems say they would have to reconfigure bus systems that use the same vehicles to shuttle students to different schools at staggered times. Critics contend that change also would involve high costs and conflicts with sports practices, after-school jobs, extracurricular activities and family child-care arrangements.

“If it was an easy fix, everyone would be doing it,” said Bob Mosier, spokesman for the Anne Arundel schools system.

The discussion about adolescent sleep and school openings dates to at least the 1990s in the Washington region; Arlington County voted to shift its start times in 2000.

In Fairfax, the issue took off again in April, when the county’s school board voted to establish a goal of start times after 8 a.m.

In Montgomery schools, interest burgeoned in October with an online petition calling for start times of 8:15 a.m. or later, which got more than 10,000 signatures. A work group created to look into the question has now met several times, and recommendations are expected by June.

“The goal is to make sure everyone has as much information as possible about the science” and data, both to understand benefits for teens and the impact in school districts that have changed start times, said work group leader John Matthews, a retired transportation director for the school system.

In Anne Arundel, parent Heather Macintosh delivered a petition with 3,500 names in January, asking the school board for later start times. Macintosh is co-leader of the Anne Arundel chapter of Start School Later, a national group based in Annapolis.

In February, the school board asked Anne Arundel staff to put together a report with details about possible changes, issues to consider and costs. The report is expected to be ready next week and will likely be shared with a citizen advisory committee as a starting point, Mosier said.

In Howard, parent Mark Donovan formed a chapter of Start School Later in January and is part of a petition effort for later start times. He said he was inspired by Montgomery’s efforts and his observations as an adolescent counselor and father of two. “Kids don’t function without 81 / 2 or 9 hours sleep,” he said.

Howard officials had already taken an interest in the issue, and the school system is examining issues related to transportation and cost. If the idea appears viable, Howard will embark on a second phase that will include seeking community input, spokeswoman Rebecca Amani-Dove said.

“My hope is to help the school system make this change,” Donovan said. “This is something I’ve wanted to do for years.”