I'll tell you why
The reason why schoolchildren are being subjected to unnecessary biometrics (and it *is* unnecessary; a school is an environment where everyone really does know everyone else) is to prepare them for not having such a thing as a private life when they grow up.
Condition them while they're young to show IDs, give fingerprints and accept authority without question -- that's what the government want. And of course no private firm is going to turn down the opportunity to be a monopoly supplier of something that eventually will be made compulsory.
A quick glance at this timeline of events shows the true extent to which Britain has become a nation of pathetic, cowering sycophants who will put up with anything the government throws at them, then crawl over broken glass to beg for more of the same.
1984: Miners' strike. Huge popular sympathy for the striking workers.
1990: Poll Tax. Popular sympathy for demonstrators but some people just tutted quietly and paid anyway.
1993: Criminal Justice Bill. Noticeably less sympathy for demonstrators than 1984; eventual passage of Act (in 1994) seems accepted as inevitable.
2000: Fuel Protest. Outraged voices peter out and blockades are lifted after a few days. Britain stops tutting quietly, returns to work.
2007: Smoking ban. An Englishman's home is no longer his Castle as the government seeks to disrupt lawful acts taking place on private property, running counter to the letter of the Criminal Justice Act 1994 (see 1993 above). Sanctimonious non-smokers gush about how wonderful it will be to have a pint without coming home smelling like an old ashtray. Even smokers seem to think it might give them the fillip they need to give up. Ordinary non-smokers prefer being rained on outside pubs with the smokers, while a few people inside sip mineral water and complain about the smell of stale beer and body fluids.
2007: Schools taking fingerprints. Compulsory ID cards for all. Fuel price breaks £1 barrier. And all anybody does about it is tut quietly, or blog about it (until they get a takedown notice, then they remove it and apologise).