“lesschumras, joint operation is nice, but brings up other issues.
Who do you allow to join this venture? Is it any Jewish school? Does that include reform and conservative? If no, where does the line get drawn? Some people on this site don’t think MO fits into the orthodox category, so its a very touchy subject.”
It’s not a question of who do you allow. You could have multiple ventures( i.e one for MO,another for chareidi, another for yeshivish etc ).It’s up to the schools themselves. In any event, the venture does not depend on hashkafa. In one example that I am aware of, one school is yeshivish, with separate ( 2 miles apart ) boys and girl’s divisions and the other is a MO coed day school. They have one dinner ( saving expenses , and it held in a manner that satisfies the yeshivish yeshiva ) and share all expenses proportionally.