I think this is where the culture differences come into play because a martial arts school would simply not be allowed here to run as after school care. All afterschool clubs and childcare are regulated here by OFSTED and have to abide by standards laid down by the Dept of Education as well as be inspected yearly.
Martial arts to us here is mostly a sport alongside football, athletics etc or even a hobby, having it as childcare is something we wouldn't really consider, most classes here are for an hour a week, perhaps an hour and a half, where martial arts techniques are taught.
Well most children's classes are like that but there are posters who have said it's mostly games etc rather than actual martial arts taught at 3/4. My opinion has nothing to do with whether they put their skills to use or not, especially as they don't seem to learn any martial arts techniques, my objection is having classes of children as young as three. If it's for physical exercise etc then that's what it should be presented as, perhaps a 'toddlers gym/ready for martial arts' class or suchlike rather than a martial arts class if they aren't actually doing martial arts.
This is representative of the UK on the whole, the Budokwai is a very old club, they have a class for 3 year olds but it is not a Judo class, it's called 'Pre Judo class' they don't teach martial arts. They have a 'Judo Gym' class from 6 months+ but for parents/carers and their babies again not martial arts. this is the type of class that is useful and suitable for toddlers, along with their parents/carers rather than unaccompanied in a martial arts class.
http://budokwai.co.uk/judogym
but I'm thinking as has been said this is a cultural difference as much as anything.