schooling

I have a question for those who live in the UK and have children who have recently been in year one at school. (let's say the past... five years) What is the curriculum like? What might a typical day be like for the kids? I ask because my Mother inlaw had these concerns that somehow Senor Onion might be behind when he starts school. Right now he is in preschool. (since he was four when the school year began) I think preschool is like the reception year fromm what I am able to gather. Now from my perspective, it seems like year one is like Kindergarten in the United States. Obviously more structure than preschool (he is in a play-based learning co-op) but probably not SUPER hard-core academics.

Any other thoughts/opinions would be appreciated.