How old do you think children shall be when they start at school?

In Norway there are a discussion about when children should start at school. The minister of schools would like Norwegian children to start at school when they are 4-5 year old. I agree even that I don't vote for him. My experience with my own children are that when kids play with words, they have fun, and can start read early. My youngest daughter was reading when she was 4 year old. She could spell small words when she was 3. But most people in Norway don't want this change! I can not understand why....