at 10 months our DD had:
waking up -breast milk
breakfast - solids using small amount formular milk
10 ish - snack [fruit, biscuit etc, drink of water]
Lunch - solids
3 ish - MILK, breast if mummy home, formular is at nurseyr or with daddy
Tea - solids
Evening feed - breast then formular [so daddy could put her to bed]
I was unable to express [don;t know why but had lots of hel and tried very hard!] and decided that some breast milk when I went back to work was better [for us] than all formula. My supply changed appropriately. I too work in school and found expressing not really possible..... [Hmmm "Miss, why have you got your boobs in a machine?" etc.}
We used Hipp as it was the only one I could stand the smell of, was cheapest per 100g and had recyclable packaging. [cardboard ot tins]
Its a worrying thing to think about going back to work, we were worried about feeding and stuff. However we all settled really, really well, helped by practise days [dd went to nursery and I popped into work before it was actually officially time]
You and your dd will be fine and you should be guilt fre and you have given your daughter as much breast milk as you could. I was still able to feed till dd was nearly 2