Good luck trying to enforce an agreement on 13 year olds who have signed without the knowledge or consent of their parent or guardian.
Sure, you can have a piece of paper in which a minor commits via contract to do x or y, but you find, when they don't do it and you go to court to try and punish them, that they're minors and you can't hold them to the contract. But they CAN hold YOU to it.
Notice that the author's use of the term confidentiality agreement was enclosed in parenthesis.
No one (not even the author) thinks it's an enforceable contract.
The language was chosen to maximize the response of readers - consider yourself maximized.
Actually the contract is identical to what a child molesters does...
Think about it!
"This will be our secret..."
"Your parents would not understand our looooove...."
These people should not be in public school, in a court of law they would be facing attempted sexual molestation and be put on the sex offender database.