I am a closeted high school senior (I refuse to disclose the name of my school for privacy reasons), and I am definitely not coming out until at least college because high schoolers tend to be really immature. I am already out to my parents and a few other trusted adults. I am only out to one other high schooler but he lives an hour and a half away from me (he used to live near me), and he's also bisexual and he swore me to secrecy and he seems to be doing a good job at keeping my secret. I have several other friends who are gay and bisexual and I'm not even out to any of them except this one guy. At what point in college do people usually become more mature and accept LGBT people more?
Everyone progresses differently. There's never a single moment that one person changes from immature to mature. Maturity is a forever-evolving thing. Some people never do fully mature, and some people mature early on. It is not defined by age or status. So, there's really no answer to your question. You'll have to find the mature ones on your own, and judge for yourself who you feel would accept you. But also, don't be afraid to branch out and be trusting.
Personally, I have met Highschoolers who act like 30+ year adults. And I've met College seniors who act like they are in Junior High. I've met professionals in their 40s who conduct themselves like 19-year-olds, and 23-year-olds that spoke and acted like a mature, responsible, and respected individual. Do not let how others act hold you back from being open and expressing who you are.
Acceptance of another person's traits is not a question of maturity but a question of willingness. Scientific studies have shown time and again that prepubescent children are not born hating anyone because of race, sexual identity or religious involvements. Instead children are taught to develop the hate or distaste for certain things while being accepting of their own position by their outside influences. Maturity and wisdom allows one to cast off perceived notions of what is right and wrong to an individual but does not mean an automatic acceptance of everything they were taught to reject and may in fact reinforce their accepted basis for deciding something is indeed distasteful to them. If you are holding back expressing who you really are believing a place of higher learning will be the root of your salvation you may be in for a very rude awakening when you get there because, shock of shock, not all colleges and universities are all too terribly gay friendly.
