Found this this morning.
There is no law against photographing or filming children, provided the images are decent in nature. It is still wise to obtain permission, if possible from the parents. When you ask for permission to film children it can often be useful to keep the camera running when that permission is granted. You then have a record, in the event that your filming is challenged again later. Schools, which are private premises, do usually forbid it. So be sensible. If your filming upsets someone try to calm the situation and, if necessary, stop. Be careful about filming in "prohibited places" without permission. Typical prohibited places include military establishments, aircraft and ships, most airports, naval dockyards and many telecommunications centres. You may be challenged by security forces. Once again a polite explanation of what you are doing and why may well resolve the situation, but you may be told to stop.
Fair and common sense.