For an entire group that needs work/is beginning, I'd do this. Even if they were doing okay using a board I'd at least go back through and only "pass" out of that station the ones who are still doing it well. Otherwise they need to get it way good there before moving on.
Try two springboards front to end in front of a crash mat. Have them do small run, good bounce to bounce, straight jump stick to perfect landing position with hollow core, correct arm, strong knees and feet. See if their landing position can resist downward pressure, side to side. All muscles tight.
The two boards makes it so they will obviously mess up if their chest is down, hence starting with straight jump.
Then I'd probably move them to tuck jump with correct corresponding downward arm motion. Make sure landing is still "perfect".
You could move it to dive roll at this point but I guess I would just let the good ones go to tuck. If they don't have chest down problems then I'd probably move them to punching off/landing on a good 4 incher...little more bouncy than just the floor if you have to stay tight and punch hard, softer. I love front tumbling all on 4 inchers. After that, punching off a sting mat onto a 4 or 8 inch...then sting mat to sting mat. Then floor to sting mat (if one of the problems is visually assessing where the punch is in relation to landing mat - sometimes not a problem when the skill is taken floor to floor - you could put a small carpet in front).
another good thing for leg power/punch speed is can they do a couple good pike jumps moving forward (3 or 4). The pike jumps force you to move your legs fast and punch tight.