I’m a school teacher in the Philadelphia area, seeking information on school gardens.
Have you looked through the subject guides we've put together on gardening with children?
Go to the main subject guides page and click on "Children"
Suggest you look at Arden Bucklin-Sporer. How to grow a school garden : a complete guide for parents and teachers / Portland, Or. : Timber Press, 2010. We have it here in the PHS McLean library both as a print book and an eBook and I'm attaching a chapter for you, with lists of easy school garden crops.
As far as a guide to "what to plant, with what else," I'm assuming you are planting a vegetable garden so I suggest you look through the subject guides on Vegetable Gardening.
There are many good titles here, like Niki Jabbour's The year-round vegetable gardener : how to grow your own food 365 days a year no matter where you live
And Brennan, Georgeanne,1943- The children's kitchen garden : a book of gardening, cooking, and learning
All titles are available in the PHS library.