I had my first major bipolar episodes at 14 and 15 years old. It definitely affected my behavior at school, and everywhere. That was over 30 years ago, though. At my school in the US, once the major problem really showed itself, my guidance counselor took over advising my parents. I don't know if you're the equivalent of a guidance counselor or if you have the equivalent in Australia.

In the US, it is/was my assumption that such a school official has/had a protocol for handling such matters. In any case, the very first step was to strongly encourage my parents to get me to a child therapist. If your student takes medications, I'd think that a psychiatrist, or other psych medication prescriber, should also be notified about the student's issues at school. In my case, my parents had to do that. I don't know if some schools now have formal mental health counselors that can take such initiatives. I never had children.

In my youngest nephew's case (and even my brother's), the schools referred to a special school. Both eventually returned to regular public schools.

I recall at a point when I was clearly depressed, a guidance counselor tried hard to find classes for me that I would derive more satisfaction from. That helped a little, but not enough.

I sort of like your idea of a coordinators pass, but with some reservations. My reservations are if the student used that private time for harmful behavior. Like others, I am not sure being at the front of the class is necessarily best. Perhaps ask the child if he'd like that. Sometimes the back of the class is better.