Get this for your schooling:
http://www.rei.com/product/833115/or...single-pannier
and this for your groceries (maybe x2 if you don't get that backpack):
http://www.rei.com/product/825299/no...e-bike-pannier
That last one is touted as the best bag of it's type because it is very strong and supports the load well, while still going on/off very well.