Hi,
Yes all children go to school at 3.
It seems young to us but it is the norm here. They start at their proper big school in the nursery dept. in the Sept. after they are 3. It is free in state schools or very cheap in private schools. The law states that your child does not have to go to school until they are 6 but if you chose not to send them until then, they would have missed out on allot of socialising and language learning and may not even be accepted in the chosen school as places may be limited.
Formal education does not begin until 6 years old though, so the early education is social and not the 3 r’s.
When they start they go for mornings only and then full time. Many people only put them in until lunch and pick them up before ‘comedor’. It is up to you if you return them after comedor.(well it is here, dont know if it is where you are or in private schools)