An excused absence does not mean that it does not count towards the 90% rule. It just means that they have a valid reason for being absent. They still will have to make up the missing time.

An excused absence only applies in terms of truancy.

Furthermore, the only valid excused absences that do not require the time to be made up are court, medical hospitalization, religious, or bereavement.

For example, I had a kid miss eight of 10 days just like you were discussing, and the campus was sending out truancy notices. Turns out the kid was battling cancer and was missing because of chemo treatments. That seems to mean to be a pretty valid reason for not coming to school.

There are lots of good reasons students missed school. There are lots of poor reasons as well. That’s why there is an attendance committee whose job it is to look into those reasons. If you are not on that committee, then don’t worry about it. Just teach your band.