Reference article
School (Level 3)
School level 3 has room for 3 students at a time. Each lesson takes about six minutes.
Upgrading it
Upgrade 
2 through the 
Upgrade Well once the Well reaches 4. Have the supplies below ready and finish construction before using the new level.
Studying
Choose up to 3 ducks with at least one racing grade below S. Return after the lesson and graduate each student to improve one randomly chosen eligible grade. Upgrades add places rather than shortening lessons. A student is unavailable for other activities and does not earn sleeping rewards. Replacing it before graduation loses its lesson progress.
