Actually they ended student deferments when they switched to the lottery system. I was a 19 year old student and drew a high number also.
Student deferments ended in Sept. 1971 . Trump graduated in 1968 which means he could have gone for his Masters and got another deferment . BTW , I was 19 in 1971 . My number was 140 . Fortunately for me the highest number they took was 95 .