My boy is 4.5 and so tired starting school,any advice?

he has meltdown tantrums from when i pick him up to teatime or bedtime.you can see him crumbling with hunger and tiredness and i have trouble coping with him and my 2yr old twins.i offer snacks at pick up but he has gone past the point and throws it on the floor.am trying to keep him off one day as i really think its too much for him 5 x eight hrs days out of the house.not sure the school is on my side though.anyone been here before?he sleeps from eight till half six currently waking once in the night which have never been able to break.