RYochananWannabe,
Several points:
“send me to a school which is against the SA(EZR 21)”
We don’t pasken from the Shulchan Aruch; we pasken according to today’s rabbis. Rav Soloveitchik z’tz’l, who qualified as a Gedol HaDor, was an enthusiastic supporter of co-ed schools, founding one himself in Boston. Your father is an Orthodox Rabbi and absolutely can follow Rav Soloveitchik’s position on that (and on anything else). When you get semicha yourself you might pasken differently but you have no right at this point in your life to question that! To doubt your father’s decision here may have put you over the issur of Kvod Av!!! Rav Soloveitchik was also an enthusiastic supporter of the idea that Jews need to have the best secular education; not only did he have an earned doctorate, but so did his wife, his son, both daughters, and both sons-in-law! All of them have remained completely dedicated to Torah and have inspired many thousands of Jews. Your father may well identify with that hashkafah.
Once you accept that you are bound by your father’s psak, you should have a discussion with your father. Many MO communities do have a lot of people who are lax in observance of some important mitzvot. I know because I myself am in one of those communities and I try to be an example to inspire those folks! There is nothing wrong, however, with feeling that you are a better fit for a community that is on the whole more careful with mitzvot. But you will never find a perfect community so be careful lest you set yourself up for disappointment. Be open minded that your hashkafah will not be the only legitimate one, and accepting about the fact that not all Jews are fully observant — yet. May your life become a model to inspire all Jews. Good luck!