The other side is that children learn there is an intense adult response to certain topics. That may lead to excessive interest in that topic. Or ever more secretive behavior. Or an inability to challenge authority.
On one side of the balance is maybe a student's life. On the other is more students' mental health and autonomy. Life usually wins, but only history can judge whether that's wise.
The monitoring for safety argument is merely an excuse to eliminate the right to privacy and shift the power to a government entity. Never in the history of mankind has this power ever been abused.
If this were possible schools would already be doing it.
Meanwhile, the article is about third-party data slurpers sitting in between the school and the Chromebooks that are supplied to a captive audience of millions of minors. The tradeoff here isn't between security and freedom. It's between whatever security the third-party claims to deliver and the risks from what the third-party actually does with the data to turn a profit. We have to gain insight into that fundamental question before we can begin reflect on your point.