AITA for using reddit to vent about being bullied and my overall awful mental health?

I got suspended from school over anonamous reddit posts that used no names of anyone involved or which school it was. I didn't even use my own name. One of the posts they presented as "evidence of wrongdoing" was literally titled "I want to KMS ATM" and describes how I'm being bullied relentlessly by my teacher. Again, i have to stress here, the account was completely anonamous. I did not use my real name, any identifying information of myself or the school or anyone else, not even genders. I just used it to vent and release the stresses of the day, and maybe get advice on how to deal with the situations I'm going through. I did not openly adverise this account and I turned off the ability for people to follow me. Unfortunately, this was before reddit put out the feature to hide all of your post history, but you better believe that I'm using that now.

The school have completely neglected their duty of care for their suicidal, documented autistic student, but I'm being told that I'm in the wrong, not them.

So reddit, morally speaking, AITA? Have I actually done anything wrong here or are the school just trying to cover their asses? AITA?