The special classes run on a 6 day rotating cycle. 
I've listed our specials below so you can help your child remember to wear sneakers on gym days:
Day 1 Music
Day 2 Physical Education
Day 3 Art
Day 4 Music
Day 5 Physical Education
Day 6 Library

I know this rotating schedule can be confusing. I found writing these on my daughter's lunch menu helped me keep track of them at home.