this how do i do this?
Use overlays and layering.
what overlays ?
The classroom tables. Check if they exist in the art catalogue, if not, you need to make them/have them made.
I’ve got them what layers should i put them on?
Well it depends on your scene structuring. But you need to position people behind the tables. So for example the back row, have student at layer 0 and table at layer 1, next row character at layer 2 and table at layer 3 and so on.