For me it depends on what we do after school on the days DD is not at the childminder. Saying that, we eat dinner together as a family at 7pm, so a decent snack is vital for her. I never saw the reason behind cooking at 4pm for a child, feeding her a snack at bedtime and cooking again for DH and me. Far too complicated and time consuming.
Normally I don't take a snack with me if I drive as it just takes 10 minutes and she sits in the car. If we walk I bring her something but then she eats a healthy snack at home like a slice of bread with fruit.
If she goes anywhere directly after school (tutor or club) I bring a packed snack with sandwich, fruit, a treat and a drink. Basically what she would get a home as well.
At her childminder she gets cooked tea but only a small portion as she gets full dinner with us.
I find a school cooked lunch ridiculous. The portions are tiny, especially for the upper KS2 children like DD. Also DD never is/was a big lunch eater, regardless what or where, she will not eat enough to last for 5-6 hours. So not each child is the same when it comes to the fact how hungry they are when leaving the school.
Junk on a regular basis is a big no for me. Our school has cake sales virtually every Friday plus in Summer ice cream sale. Luckily DD comes out 30 minutes later as she attends orchestra so misses it most times and I am never that early to buy her something. I do it once in a while as a treat but not every week.