Be creative. Make some exercises that force them to watch the drum majors hands. Have the drum major have a met in headphones and then conduct for them. You could count them off like 8 clicks from a wood block then go, but then have them do the exercise in complete silence. It'll condition them to watch for time and hopefully be more together. My guess is that right now they are listening for time so this will be rough at first, but in the end its a great fundamental exercise for timing and will help them lots on the field.