What to do about this guy at the yard?

theres a boy at the yard who has had lessons since last july, he is a kind enough person but he just thinks he knows EVERYTHING about horses and riding. when new horses come he has to give me and my friends a lecture about the breed of horse and where it originated from and everything, and its usually wrong, and when people are riding, he will say there on the wrong diagonal, wrong bend... when they are right and he cant do them :/ he also rides a 13.2hh pony and he is 6ft tall! he can walk and trot, but says he wants to get either an ex racehorse or a shire horse :| ugh he just thinks he knows everything and one of his ancestors was in an american tribe, he thinks he is a natural and its in his blood. its starting to bug me :/ what can i say to him without him being offended? thank-you for your help!! =)