My DS is 5 on the 25 June, I can honestly say despite thinking he'll be fine it has only been since the start of this Easter term that he seems to have got to grips with the institutional life that is school!
He loved preschool and went every afternoon, I never had any problems settling him in to preschool- he was ready for it, had enough stamina, was very sociable so I thought school would be fine. Also, I thought the school was going to be focused a lot more on play but it is far more academic than i imagined. He just found the whole thing overwhelming - the reception year had 120 students, the infant school is big and the expectation of what they could do for themselves was very removed from nursery school.
My DS is one of 2 boys that are summer born, there are 5 that are Autumn born and 3 that are spring born. This has had an impact on his confidence because despite being popular, he is often told by the older boys that he is small and therefore can't be certain roles in lunchtime games.
Academically, he is very good at maths and his art and written work is very good apparently but he is average for reading. Despite this the teacher relays to me that I need to apply pressure with getting him to be consistent with key words. He is still only 4 and this kind of homework seems very full on. She has also said that he is very slow at everything- he is often the last in the canteen eating his lunch and often doesn't get to finish it. He lost weight as a result and at one point around Christmas looked awful, my whole family remarked on it.
Anyway, IMO and having heard other mums with summer borns, those with girls aswell have similar experiences. To be fair though my NCT friends whose children are at different schools are doing really well. One I was really surprised by as he is very young in outlook and quite introverted. However, it is a small village school so perhaps more suitable for a smaller child.