Nice idea and I'm sure some kids in UK schools will enjoy learning with this device and who knows, inspire someone to be a great programmer.
I do have my reservations though - it'd be like giving a kid a 56kbps modem and asking them to surf the net with it. I just can't see many having the patience to learn code with how kids are these days wanting everything 'instantly'. It's a far cry to when many of us were at school and computing was 'fun' and in that age when people were 'really' interested in programming and how these things worked!
Can you imagine a Facebook update 'wowsers I just made my computer print screen on a loop saying 'I am cool' with my 'Raspberry Pi'... nah.