for ms in Class/*/*/*/MarkSheet*; do
find "${ms%/*}" -type f -newer "$ms"
done
With your approach, you need to a shell to expand the MarkSheet* glob. So:
find . -mindepth 3 -maxdepth 3 -type d -exec sh -c '
for dir do
find "$dir" -type f -newer "$dir"/MarkSheet*
done' sh {} +