To clear it up......each box will have the same 12 DIFFERENT blocks out of their fabric. Then it's up to each person to put their blocks in their box together any way they choose, for show & tell.
Basically, is it good to say 6 colors (1/2 yd. each) plus 2 yds. background color? Does that sound about right? They should not run out this way. This would not include backing or binding. And they can add border colors later when they put the quilt top together.