You want to go to some land far away and say i.e. fly a leg each to cost share. Only one is a member of the school. The membership here I am presuming is paid for insurance purposes, upkeep of facilities etc.
In real life they will both have to be members of the school, because the school won't hire you the aircraft on any other conditions. So. two people who are members of the same school/club, fly one leg each of a landaway, change seats before coming back if that's the club rules, each logs their leg as P1.