It looks like when the score hits 100 the student is using a sprite for the background instead of just relying on the
background() command. This means that the background sprite is getting drawn with
drawSprites() on line 78, which is after the score is being drawn on the screen. I might point the student towards the fact that they're using a sprite as the background, and how that changes the order in which the background shows up in the stack. From there they should be able to move the code that draws the score and move it after
drawSprites() in the draw loop.