Why not just make school a more attractive place to be? That way they wouldn't need all this expensive technology just to make sure they're getting children through the gates.
One of the worrying implications - the fact that it doesn't seem to occur to the teachers in favour of the proposal that it would be pretty straightforward for pupils to fool the system. If teachers really think the kids are not bright enough just to give their card to a pal, why aren't they wondering what on earth they are doing with their time?
On the other hand, if the card is made user-specific and with a slightly greater range, that really could spell the end of the secret liaison.
HT: Arch Blog