It depends upon how much effort the sim has put in.
The easiest way to find this out is to check the FSS Word On The Street once it shows up (or check it now if it's already there - it shows up some time during the 2:00 hour EST both am and pm).
If WOTS says something like the recruit had some interest from the sim school but is open to other offers or says he may not be a priority for them, it won't be too difficult to put in enough effort to steal him.
If, however, the WOTS says something like the recruit is "a very high priority" for the sim school or the sim school "is very tight with" the recruit, you can still beat out the sim school but it will cost you considerably more to do it.
Remember, sims do all their recruiting before human recruiting begins, so once you put in enough effort to take the lead, the guy will eventually sign with you.