For some reason I just don't believe the article as written. I suspect she took the chemicals without any permission, and the "experiment" was more in line with "oooo, chemicals, lets mix them together randomly".
Similarly, drano bombs are "dangerous" and "exciting".
Seems the "science experiment" part was just a cheap excuse, to try to get a free pass. Ironically, it may have made it worse for her..
I did similar things as a kid, just not in school. Bad judgement, but expelled from school and facing trial is just ridiculous.
If my kids were in that school, I'd seriously consider moving.