Well done to Barry Sheerman for bringing up the awful situation many teachers face when they are accused of doing something wrong by a pupil (or sometimes, sadly by another teacher or classroom assistant). In the vast majority of cases, the accusation is trivial and has been made up by a wretch looking for revenge on a teacher who has confiscated their mobile phone, given them a detention or thrown them out of the classroom for being a pain. There's an article here
In every case I ever saw, it could all have been sorted out in less than an hour if all parties involved had been immediately interviewed by the Head. If a child is making false accusations then they need a severe punishment and if it looks like the teacher actually did something seriously wrong then the police could be involved.
What actually happens is that the unfortunate teacher gets suspended whilst a tediously slow 'investigation' is carried out. Months later when the pupil is found to be lying there is no comeback on them, so they cheerfully do it again.
(Incidentally it's not uncommon for pupils who have worked out how the system operates, to threaten to make a complaint against a teacher, when for example you attempt to remove their MP3 player. It' a very effective move)