Reference article
Stage (Level 4)
Stage level 4 lets one teacher train 6 learners together.
Upgrading it
Upgrade 
3 through the 
Upgrade Well once the Well reaches 7. Have the supplies below ready and finish construction before using the new level.
Teaching your flock
Choose a skilled resident as the teacher and seat up to 6 other ducks as learners. The teacher has a separate place. Learners improve racing skills where the teacher is ahead of them; 
Energy still comes from feeding. Upgrading adds more learner seats.