What’s your procedure for students that need to use the restroom during a marching rehearsal?

Our practice field is a distance from the band hall, and the band hall restrooms are the closest restrooms to the practice field.

A student went to the restroom during an outside marching rehearsal and made an unfortunate choice. I got flack from admin because I should have been monitoring better.

Currently, students that need to use the restroom let a director know and then they can go.

Is there a better way without losing a ton of rehearsal time or taking staff off the field to monitor the restrooms?

It’s only me and the asst director. About 120 students.