Much easier to get a robot ...
to monitor children than for adults (teachers in this case) to know what the kids in their charge are up to.
What kids need is to trust adults and be confident enough that they will seek guidance Adults should spend time with them, adults should get to know and care for them -- and the kids be aware that they are being cared for. A computer is not a substitute for that.
Also: kids will get up to a little mischief, and have done so for millennia, it is good for them to push boundaries, to explore as they get older. Feel the consequences of going too far. What about the perve from the Internet I hear people say -- that is what you need to build adult/child trust for -- so that the adult will get to know and so react/guide in what is really a relatively rare situation.
Sexting: education as to why it is a bad idea, then support/admonishment when it does happen. Making criminals out of kids for this is over the top.
Bullying: this is not new, on-line bullying is just a development, just as when kids stopped using slates and started using paper in the classroom.
Naughty pictures on the Internet ? A natural curiosity. 'No' is not the answer (& impossible to achieve), but educate the differences between sex & relationships, romance & love. Not new anyway -- in my day it was smuggled copies of Playboy.
All of the above need adults (teachers & parents) to spend time with kids, get to know them.
The trouble with a solicitor driven risk averse society is that kids are not allowed to be kids.