I assume you have been down the road of finding out why the child is badly behaved, could be one of many or multiple factors giving rise to such behaviour.
If the behaviour of the child is already an issue why attempt to give him/her the skills whereby they could physically incapacitate anyone that challenges any future bad behaviour ?
There is a well run Ju-Jitsu club in Accrington that may assist you, however it is very well subscribed. It is run by Max Robinson who is an excelent teacher/mentor. The club is usually run out of Oswaldtwistle community center.