Not at all sadly.
DD used to do breakfast club from 8am then afterschool club till 6pm, in the summer that was followed by best part of an hour in the park and then a 40 minute bus ride home and was still going strong, and rarely in bed before 10.30pm. She now only does 9am - 3.30pm but everything else is the same.
I'm the one who is exhausted.
She's now in Y1 and I had hoped that the more formal structure might tire her out a bit more, but it hasn't.
Personally, I think it totally depends on the individual child. DD's not hyper-active or anything like that, at home in the evenings she's spends hours colouring or quietly playing with Lego or other toys, she just doesn't get tired and doesn't appear to need more than 7-8 hours sleep - she's never whingy or falling asleep during the day. I think she's probably not the norm though.
I had no concept of children who got over-tired or who suffered due to a late bedtime till I stayed with my sister for a week. I think that is perhaps more common.
She did go to a primary school nursery which was full-time, 9am - 3.20pm from when she was 3.5 years and none of the children had problems with the long day after the first term. There were bean-bags in the corner if any of them felt like a nap. Reception had the bean-bags too.
Children who need to be in bed by 7pm, will probably find it pretty exhausting for the first term, but they do all cope and schools are very used to the little ones getting tired.