just wondering

I found myself wondering what the difference is between a church that acts like a school and one that acts like a mission?
 
Is it a numeric difference?  Is there a percentage of folks on board that makes it go from somewhere where you go, sing a bit and listen...to some place where you meet up, strategize and go out?
 
Would 50% make it a mission?  Maybe it's not a number at all...I'm just thinking writing out loud.