Must it be "drawings on" with "s"? Why is the "drawings" plural here?

Rebecca

"Drawings" is plural here because it implies that they are drawing multiple things or multiple, separate pictures. You could replace this with "the children are all drawing on my cast", however, this would change the form of the word "draw". In the case of the sentence here "drawings" is in the noun form and if you replaced "drawings" with "drawing on", "draw" would become a verb. Ex: They are drawing on the paper. Ex: She has lots of drawings in her sketchbook.