I have to thank @papayalily for mentioning Shelby Knox – the documentary telling her story is The Education of Shelby Knox – A Documentary of Courage and Grit. It’s not the most encouraging about the practical ability to get programs going in areas where there is resistance…but it shouldn’t discourage you if you want to try.
What high school administrations use to keep students in line when they actually attempt some form of social change is, sad to say, fear. Realize that the heads of your high school may not be small-minded themselves, but they are subject to pressures from both government boards directly, and your parents indirectly. And if parents get upset about you trying to teach their kids something they find immoral, the school will very well buckle under that pressure.
However, DON’T LISTEN if at all possible. What they RELY on you thinking is that they actually have some real, permanent DIRECT effect on your life. @RealEyesRealizeRealLies brings up a great point – this will look great on your college application. That, of course, is not the reason to do it. What it tells you, however, is that threats regarding your future (scholastically and professionally, at least) may generally be empty. @Kraigmo brings up the important other side – the effect that they have on your life may be INDIRECT, through the pressure they can exert socially and, potentially, economically. This can be serious and even devastating.
What you need to research more than the logistical issues (the how of the program) are your support issues (who will be there for you). Shelby Knox had an amazing support mechanism in her family. How much have you addressed what you are planning with your parents? How will your siblings react? This may be the most important thing to consider – because if you’re worried about the community reaction, your parents definitely will be. @muppetish‘s suggesting of getting in touch with the ACLU is great, but you may want to do some research on your state bar association’s civil rights and pro bono support organizations, as well as similar programs in state or local law schools. These are, at least nominally, non-partisan organizations (if you need links and don’t want to reveal more publicly, feel free to PM). If you come to your parents with these resources, they might be more willing to move forward with you. Then there’s you – in the end, how much trouble are you willing to go through? Then, as mentioned, there are your friends – even if you don’t mention them initially, if this breaks publicly, they may get pulled into it…would they be ready for that? How will that make you feel?
What you suggest is so important. What I want to emphasize is that (1) the pressures you might be concerned with from the school are the ones the school might want to distract you with – the real pressure may be more social and economic, affecting your friends and family, so try to be on the same page, (2) your support mechanisms you’ll need most may be the emotional ones rather than the logistical ones, and (3) the logistical support you can get is probably much more expansive than you think, and more readily available (especially legally) than you might be ready to believe.