I don't think it's a lack of knowledge that is the problem here. Almost all kids are taught the basics of "be nice", "don't be a jerk".
But if someone treats a person badly, and they have the option to get revenge anonymously ... a lot of people find it hard to resist the temptation to hit back. Just this once.
I'm sure most of the students at the school do know that. The app is completely anonymous, so for all we know, the nasty comments could have been made by just a handful of students.
