I, too, remember that story Nigel--only bits and pieces, however, and sadly not enough to help you with your query. However maybe between the two of us we can jog someone else's memory. The additional detail I remember: the fugitive student is being hidden from an uncle in Africa who wants to take over the family lands and fortune after a dreadful slaughter of the new boy's family. The boy is the only survivor. Our main character befriends him and becomes his protector, a role enhanced by the main character's involvement with the school's cadet corps (? what is it called in England?) and and this leads later to identification of the new boy's pursuers while they are on a cadet training exercise. Later in the story both boys are at the main character's rather lavish family farm while the rest of the family are away, and they are forced to defend the holding from a team of assassins deployed to kill the new boy. I think there may also be a later scene set in Africa... it's all very hazy, and I'm somewhat led to believe I read it on a site like IOMfAtS. I hope that helps to add some pertinent detail to your query?