How about the Air Arms s400 MPR sporter? My 14 year old daughter has owned one for nearly 2 years and has just won the Div 1 British Sporter League with it - she also uses it for Target Sprint. I guess it depends on what you want to do with a rifle and what potential path your son wants to follow i.e. 10m precision or something else? Either way the MPR would be a good option and fits your budget.