[Mailman-Users] Members sync between lists

[Hung Phan]

Hello,

We have a couple lists: lists for individual schools and one list for the
superintendent. When the parents signup for the school, we would like to
add them into the superintendent list. When they unsubscribe, we would like
to remove them from the big list as well. Currently, we do the sync option
and discover that it removes members who signup for the big list only.
Besides from the umbrella list, is there any other option/script/feature
that will help us accomplish the task?

Thank you,