I'd say a lot of it has to do with how small the school is....and if he was "known" to the officials as a parent of a child.
I could probably do the same thing at our small, small, Elementary school because I know all the people there (and they know me) after years of volunteering my time there for my kids and now grandkids.
That being said....does his punishment fit the crime of bringing attention to security problems in the school?
There is a huge gulf between the potential danger of a known normal parent and the potential danger of a known mentally ill kook with grievances.
PROFILING, people. It’s another word for “use some common sense”.