One year I had students who had a 15 planned for the day of marching contest. They were freshman. The dates had been set the year before when they were middle school students and they didn't really realize it. Fortunately, I was able, (because the kids trusted me and I them), talk with them and they understood they would not have a spot in the show. This conversation happened during BAND CAMP in August! Both were freshman in the top band. I never placed them on the field. They accepted that. They came to every rehearsal and went to every game. Went to every contest too except that one. By the next year year, I had the kids understanding that the 3rd week of October was a bad week for anything and families actually started scheduling things in November or September. Communication, not frustration fixed the situation. Dress fittings I was usually able to get the kids to do that after rehearsal.
And FFA and Volleyball are real conflicts in the fall. Kind of like football. Maybe be glad your kids are in other activities. I was as a student. I did band, choir, orchestra, pep band, cross country, swimming, and golf. And I"m better for it because my director didn't tell me to choose band or quit.
They aren't just lazy. Some of them are but I bet the ones doing other activities are far from lazy.