You can go check on Google street view... If your old school still exists!

Two of the three elementary schools that I attended do exist. They look to have either gravel or light-colored fill of some kind under the playground structures. They aren't the same "monkey bars" that I used, but there are still things to climb on.

I think I remember from a decade or so ago (when I went back to my home town last, for my dad's wake) that the surface under the play structure was some kind of rubberized solid surface. I don't think it looked like gravel the way the street view pics do.