7 yr old son doesnt care about santa?

my 7 yr old son says he doesnt have to be good b/c he knows santa will bring him presents anyway. any suggestions as to what i could do to have him beleive? i kinda want to not give him his presents and just give him coal. when i asked how he would feel if that happened he said he would go be a train conductor w/his coal!? i just wanted to see if anyone had some ideas as to what i could do to make him care.