cassbegg

Hi guys looking for a bit of help . My 13 year old has been saving his heart out for a trials/ off road bike he is about 5foot 9 and 12 1/2 stone he has never been on a bike before but i am going to teach him . i am a road bike man so little to nothing on off roaders. can someone point in the right direction off size /style for him. The only advice i have been given up to now is to avoid cheap jap copys.