Going into a school as a vistor should be OK and you should not need CBR clearance but if you intend to keep going in, say weekly, then you will need it.
I think that it is great to get youngsters interested at a young age. Pigeon racing can be tied in with the curriculum in many ways: Geography- flight paths, Maths-distances, velocities, weights,
++cost of feed, numbers produced breeding etc. etc, History- pigeons in wars, Science - life cycle of, looking after animals, what living things need, RE - Noah...... Oh, I could go on and on.....yes, you guessed, I used to be a teacher!! ;D ;D
Well done you, good luck.
Sue