Is this feasible, or even possible?
Unfortunately, this would not work. Mifare DESfire chips are high-frequency (HF) RFID transponders with a read range of about 3 feet. You could have students place their cards near a reader located at the doorway and take attendance in that way—but if a child forgot to place his or her card within 3 feet of the interrogator, that student's tag would not be read and he or she would thus not be identified and marked as present.
—Mark Roberti, Founder and Editor, RFID Journal