As a parent, I would hope one would take the time to get to know the principal. I know my kids' principals well. That should tell you all you need to know.
One problem though. In loco parentis. You can't tell the school they cannot question your child. When you leave your child at the school, you accept their rules. Imagine if every parent did this. I would not want my child going to that school, because it will be overrun with bad behavior, and the school would be powerless to enforce rules.
Again, common sense. Get involved in your child's school and help make it a better place. If you leave it to others and give no input, you are at the mercy of people who think zero tolerance is a good idea.
For some of us spending enough time with the faculty of a school to get to know them is almost impossible...
Second I think you are reaching with your interpretation of In Loco Parentis... Even LEA do not have the privilege that you assume that you have under that. I would highly advise a child to not talk to either a LEO or a School Faculty Member without a Guardian or Legal Representation being present.
Once again, Common Sense not all people have the time to know the people who are employed in their childs education...
It is very difficult to be involved in a childs life let alone his school from 7500 miles away...