Re: Gi pants leg and sleeve
When purchasing a hakama, one typically measures from the waist to the knob of one's ankle. There will be a little variation in final length from that depending on how it's tied. And one would then set the gi pants length a little shorter than that.
With that said, if a student can't figure out for themselves that pants dragging the ground are dangerous, you may have an awareness issue that needs to be addressed, too.