Without it having already happened you can't give an example, by the time it gets to the point examples are available it's too late.
See above.
The school decides to do a thorough monitoring of her activity and links her main identity to a secondary handle she is using to keep her identity secret while looking up information and asking questions on forums. Is it possible someone else might find this information yes but not as likely as someone that is getting paid to look for it. Now in the process of the company reporting this information to the administration another student or even a teacher overhears the conversation or sees the report lying on a desk. That person then discusses it with others. The rumor mill starts and eventually this student is found out. The embarrassment is enought to push her over the edge and she can't live with it and takes her own life.
First, this assumes the school is doing widespread monitoring and somehow perusing secondary sites and pursuing quasi-forensic connections between them and social media. In fact, it isn't:
Public content is collected and provided to school districts from the following websites:
· Twitter;
· Facebook;
· Instagram;
· Picasa;
· Vine;
· Flickr;
· Ask.fm;
· YouTube; and
· Google+.
Second, it assumes that the school will not only receive
private information, but will maintain copies of it unsecured in contravention of applicable privacy law (if a school collects public information from a student and condenses it into a private file on student activities, that is covered by privacy legislation and require confidentiality). Best case scenario there is a lawsuit against the school, worst case is criminal charges.
Third, public posts by anyone do not have an inherent privacy interest. If your hypothetical girl has posted information publicly, then it is fair game for anyone to see. Conversely, if someone uses that information to perpetrate bullying, criminal harassment, etc then we have both civil and criminal law that deals with those matters.
AGAIN-
It's not that I agree with the policy. It's that the arguments being presented are quite weak. There are many perfectly valid reasons to oppose such a policy, but slippery-slope / moral panic nonsense undermine the legitimate reasons for opposition and are easily dismissed. Arguments based on conjecture and possibility are never convincing.