The methods I know of have already been mentioned here (redshirt, rescind scholarship) but they aren't surefire. I do wish there was a way to definitely make a player stop considering you. I have been in the same situation before, especially scouting internationals. After only 1-2 scouting trips, some scrub from Poland won't stop considering me, so I look like I've stretched myself too thin in recruiting, opening me up to other coaches trying to poach recruits I actually want to keep.
How about an "insult recruit's mother" option for $10? Automatically ensures recruit will never consider your school again.