Public Schools - Kicking kids out for cannabis use - Rights issues??

What I experienced in high school was truly and honestly confusing. Halfway through my senior I was asked into the principles office. Dr Joanne Roberts asked me to take a pee test for pot with possible expulsion or drop out. I was in drop out prevention classes which surprisingly is exactly what it means yet their fundings are geared towards better students. I missed alot of school yes but the class I missed most was a freshman class and I had a serious trouble going on at my homelife. The public school system in clay county Florida essentially shut a child down halfway through his senior year while he was in a seriously fragile state due to a home life trouble. (suicidal parent is not easy for a child or anyone for that matter) If there was or is a legal recourse I could utilize to keep the public school system from ever doing this to a child I am interested in utilizing. The purpose of a public school system is not to shun a child for a troublesome life while experiencing serious hardship already. Ridgeview High School was a resource in my life that was taken away due to a teacher at the time using her power as a way to manipulate financing from the state. By subtracting students from the schools whom may bring the schools grade down they can manipulate their statistics before years end with this method of forcing students out thus landing better grade and more financing for their schools. Why else would a school force a drop out prevention student to dropout with a 3.2 gpa --- Its the absences and how they affect the schools grade... Thats the only reasoning I can come up with since even if I missed graduation I had summer schools to finish which I didnt need since I was 3.5 credits from graduation. I dropped out since I would have failed the piss test and figured I could start working and get a head start.