I’m an American who also wondered why he was in a 5-day school at age 4, but everyone on here told me that was an acceptable and normal for UK. And I also changed my mind in Andrea “at school” and believe it is also better for him, because he would be on an iPad if he were at home. For 15 hours of the day, maybe more.
Plus, he has an opportunity of getting spoken to more, listened to more, and eating something that is real and not Nutella.
My own son, started Kindergarten in August and turned 6 in September. I wouldn’t have changed a thing about his intro to school.