Alex's goose egg

How can I stop monkey's from jumping on the bed? Alex and John were supposed to be cleaning their room. We hear a thump and screaming from Alex. He was jumping on John's bed and fell on the window sill.

Here is a picture of the big bump on the back of his head. I think it's time to put the beds together to make bunk beds. That may stop the jumping, but will start a whole new set of problems.