School Incident - What can I do?

I had a problem at the school back in mid December, 2013 that ended up with me being forced by my school to finish my second semester from home. In the time I have been home (Nearing 8 months) My mother and I have seen several professionals and I have been diagnosed with MDD and ADD, and since have been on medications for both. More problems came though, from being isolated at home day after day, week after week. Because of the schools decision to punish me by forcing me to work from home, I have become very easily overwhelmed and frustrated, as well as very distraught from the lack of social contact, which has also impacted my self esteem and depression.

My question comes in here, because I would like to continue attending my schools technology academy when school starts this August, so I reached out to the head of the academy asking if I would be allowed to resume attendence. She replied stating that I could not attend, because I had been expelled. I had been told that I was not suspended nor expelled, and that none of the incident nor the disciplinary action resulting from the incident would appear on my record. So I reached out to the principal, whom told me that what I what I had been told was correct, none of it is on my record, but I would not be allowed back to the academy regardless.

My question is, what can I do/what are my rights as a student? As far as I can find, I should be able to request a chance for redemption, especially now that I have been properly diagnosed with ADD and major depression. Would the principal not allowing me back to the academy be considered discriminatory (due to the LGBT nature of the incident/ the ADD-Depression findings) or violate my right to learn/an education? I am not sure how to approach this situation, especially as the tech academy means the world to me, both in the friends I have there and in the education I can get there. Any suggestions?