I have an IEP meeting soon, any advice ?

so after...11 years... of this school knowing Im disabled and need extra help, they FINALLY wanna do something about it!!! 

They tried brushing us off when I was like 6 with a 504, which is crazy because at the age of 6 I only JUST started learning how to speak. (I was non verbal), but they also NEVER used it, and all my teachers didn't KNOW I had autism bc they didn't bother to put research into me. Fun! At this IEP meeting, I'm assuming that we're also going to have to inform the school that only...4 months ago,,, I was diagnosed with unspecified psychosis and my psychiatrist plus 2 other clinicians think that by the time I'm older I'll develop full blown schizophrenia.

 I SWEARRR if this time the school dgaf i'm gonna be so mad. Schools been making me so anxious and queasy and depressed trying to keep up w ts.