If you are asking not for yourself, but rather for a friend, this will apply to them - although you can go along with them.
1.) See if there is a GSA chapter in your school (Gay Straight Alliance). Many high schools have them, but they don't advertise them. It is a school club. 2.) Call the nearest Planned Parenthood to you, either Milford, MA ((800) 258-4448) or Providence, RI ((401) 421-9620) and ask them. Many PP's host or know of LGBT youth groups in the area. My local one has a meeting for 13-21 y.o. people every other week.
Also, if you can't come out right now, either suggestion may know of a good, free, SAFE site you can go to. And again, if you aren't yet out, it will help a huge bunch if you have a support group / network ahead of time.
Hope that will help.