If it's getting frizzy I'd try a handful of mousse and a dollop of curl cream after, then comb through. This is after washing and conditioner. I like Alberto Balsam shampoo and conditioner. My hair is fine too.
I use a wide-toothed comb only when conditioner is in hair and afterwards to comb through styling products.
I wash hair every other day and leave it loose to dry naturally.
On the in-between day I do nothing to it except pick which style to put it in. It's usually a little frizzy and needing to be tied back somehow on the second day. Sometimes that's just a headband or a half-up style, other times it's looking a little bit like a birds nest and needs to go in a pony tail or twisted and clipped.
I don't understand what you're asking re styles for school. Curly hair can go in the same styles as straight hair, just don't brush it during styling like you would with straight hair. Once you've styled it though, it won't hang the same if you take out the clips/bands/whatever as it did before. The curls will kind of "set" where they were put, even if you styled the hair when dry (although more so if you styled it when wet).
Sometimes if it's messy it feels better tied back than flying around my face, so she might concentrate better in school if she finds it annoying left loose that day.
If you're wanting her hair to be "less big" at school to minimise the chance of her catching head lice, you'll need to plait it, which you can do when it's dry no need to wet it first.
But if you're saying she "needs" it tied back for school because you (or others) think big fluffy curly hair looks untidy, then whoever thinks that needs to be less prejudiced, because curly haired people have as much right to take up space in the world with their curls as anyone does with their hair. Not calling you prejudiced just pointing out that attitude is out there. Your DD needn't be ashamed of her curls or made to feel they have to be "tamed" or made to somehow lie flat to her head, that's all.