Great to see police resources are being used wisely on investigating every joke someone posts on facebook, the pigs should be arrested for false arrest and human rights violations.
You seem quite vocal with your condemnation of the police but not quite so vocal as to what you would do differently bearing in mind it could be argued that it isn't your average Facebook joke and also that the full information and case details are not know by you nor I nor the media.
In the UK, bar the likes of the PSNI, MoD police etc, we have an unarmed service as you know so we do things differently. I do not use the OP as a sole example but when information is passed where, joke or jest intended or not,
any information is received that could be connected to a potential armed threat, it
has to be acted upon and will be done in accordance with ACPO policy and also under the command of a senior officer.
You do not know what information the police received, what people at the school may have said, what teachers may have said and indeed other information gathered so perhaps you should hold back with your quite acidic condemnation of the police before all the facts are in although I do say, and always have, that the police are not a perfect organisation and perhaps a way of doing things better will arise from this.
Alternatively, if you are so concerned and motivated by the shocking jackboot tactics of the police then take your case up with Liberty or indeed any other human rights group. It may be more constructive than slinging childish insults around on an internet forum.