Students at all Boston public high schools will soon be able to obtain free condoms at school - as long as they sit through a few minutes of counseling about safe sex - under a policy approved Wednesday by the school board.

Condoms are already available in 19 high schools with on-site health centers. The policy, endorsed on a 5-0 vote by the Boston School Committee, expands distribution to all 32 high schools and their 17,000 students.

Parents will have the right to exempt their children.

Several U.S. urban districts, including New York and Los Angeles, make condoms widely available in high schools. So do many suburban school districts around Boston.

The expansion in Boston will not cost the district anything since the contraception is donated by public health agencies, district spokesman Lee McGuire said. Schools will distribute the condoms on request, after a brief counseling session with the nurse or another staff member.

The Archdiocese of Boston issued a statement calling condom distribution misguided, but did not organize formal protests.

Bill Albert, chief program officer of the National Campaign to Prevent Teen and Unplanned Pregnancy, said parents often fear easy access to contraception will encourage teens to have sex earlier or more frequently. Studies have shown that isn't the case, he said.

"That is one they can cross off their worry list," Albert said. "The science is absolutely clear."

It's less clear, Albert said, whether students consistently practice safer sex when they have access to free condoms.

The condom policy is part of a broader wellness initiative in Boston schools, including expanded sex education, better nutrition and more physical activity for students.