Don't really understand the need for attendance confirmation. Tests (they do still give tests, I assume...) prove learning, not attendance.
Even beyond that, having skipped many lectures myself, the whole concept strikes me a "mothering" of the students. Screw'em if they fail.
That aside, other than requiring a sign-in with a live attendance taker and a photo ID for the student, I can't think of a single RFID related solution that can't be thwarted.
For instance, let's say the student actually shows up, on time, as evidenced by the RFID tag data, for the class. What's to prevent them from leaving early? Wrapping the RFID in aluminum foil will prevent the system from noting the early absence.
Please be honest, and please explain for us to whose benefit would such a system accrue? I would think that the whole learning process is an option, not some draconian requirement...