i am an employer. if one of my employees came up and told me that he wanted to go back to school for his MBA, i would be very supportive. if a guy just got hired yesterday and told me today that he was going to leave after this year for his MBA, i might be a little more peeved but even in that case, i would be supportive.
however, i would not want the employee studying for the GMAT during work time. if he / she has to do a few things during work (e.g. sign up to take the GMAT, talk to adcom, etc.) i would mind too much if it was kept to a minimum and it wasn't loud and wide open.
with all that said, things do get a little subjective. if it was a guy who is here all the time at work and has always given 100% to his job (working late whenever needed, etc.) then that guy would obviously get a lot more leeway than a guy who comes in here at 9 and leave at 5 and refuses to give anything extra because "hey, i filled my 8 hours here today".
RVD (yes, the irony is that i'm posting in here now during work hours)