The school was right. I'm a high school Algebra teacher, and you cannot imagine what a disruption this type of behavior is to a school.
After all this lunchroom drama, the kids' minds are not focused on academics at all. So you've lost half a day. Next day, kids are afraid to come to school. You've lost another day.
I promise you that an 8th grade boy was not engaged in a principled stand to fight for First Amendment rights or any such high-minded goals. He was showing off for attention, dragging the school down.
Many of you rightly complain about the poor results of public education. Fair enough, but some of us entered this field because we want to change that. We want our students to succeed and become contributing members of society.
For the record: my school has a dress code. No TShirts at all, except on special days when students are allowed to wear a school TShirt only. The right of a school to have and to enforce a dress code has been adjudicated several times, and the school districts generally win. This is a prime example of why.
If you don’t have a dress code, however, I don’t see why a most severe penalty can be given to a student who didn’t break an actual written rule, much less get arrested.