It's required in the USA, but parents can claim exemption under religious/faith reasons and still send their kid to school. They don't even have to provide proof they go to church, just saying their belief does not permit them to and signing to that effect is enough. Separation of church and state, they turn a blind eye to it, even if it puts everyone else's children in danger due to their lack of vaccination. The only other common exemption is medical, in the case someone is allergic to a vaccine, though that's rarer.