Yes, they certainly do. If you have an appointment letter and read it closely, you will see that the appointment is contigent on your continued performance in High School and your final transcript will be reviewed. Appointments can and have been revoked. This is not just an academy policy, but most good colleges/universities have the same requirements.
Hey speaking of senior year grades... does anybody know when the Academy requests senior year grades? I already have an appointment and I'm not worried about my grades; I'm just curious as to when the Academy wants your transcripts and if I should send in my transcript for last semester's grades. I have a feeling that it will be when the Academy sends the big packet in the spring (you know the one that tells you when to report, can't wait for it); if anybody as any idea on this please let me know.