Mine are age 4, 5 and 6 and they all have the same. Typically-
Sandwich, one piece of bread with ham or cheese or tuna and corn mayo or something.
Fruit, apple or banana, something like that.
Carrot sticks, cherries tomatos, cucumber, about half (or a bit over) a child's handful.
Sometimes a treat (depending how big a tuck I give them) small piece of cake, mini muffin, chocolate biscuit, something like that.
Water to drink.
They also take some tuck, a cereal bar or flapjack or something.
Usually all except the 4yo have something left when they come home.
I am aware that other parents seem to give children quite a lot more than I do. My eldest child has asked for more food, although she doesn't finish what so has 70% of the time.
One of the teaching assistants has also asked if I can give my youngest more food!
They are all with height and weight in proportion according to the red book.
They have a small snack after school, fruit or popcorn or two biscuits, something of that size.
They have cereal and apple juice for breakfast.
AIBU do I give them too little food? I don't think I do.