My teenage groups are "Same-Level" groups rather than 'Multi-Level", and I keep them moving forward together at the same level by giving additional music to those who "get it" faster. So I wrote out additional parts for Eine Kleine and gave these to those who had quickly mastered the "rest thing" so they wouldn't get bored while the others continued to work the rests.
A couple weeks later they really enjoyed the "full" sound they created when they all played their different parts together. I also used it with the elementary school groups. They were so excited about playing a group piece that had no "teacher part" and that they were making this music all by themselves.
Click on the parts below to try the arrangement with your own group students It is for 3 pianos, but you can add a 4th piano to play the melody (Piano 1 Part) an octave higher to give an even fuller sound.
Let me know what your students think :)