ask PHS

I work for an after school program called After-School All-Stars and I work at a school in North Philadelphia. This upcoming year I am planning on leading a STEM class twice a week. During this time, I plan on teaching the students information that they will need for their PSSAs. I want to provide this through the use of a small school garden. The area is pretty small but there is raised garden bed in the center. Because of the disuse, I believe the soil is dead. I was passed information from a lady named Dottie that said PHS had nutritious soil for pick up. This was a couple months ago, but is anything similar happening soon? Also, I am new to starting a garden and I want it to go well for my students. I was hoping that I could get some help on when the best time to plant vegetables is, especially for winter.
Any information would be extremely helpful! Thank you!