桃李

Etymology
The figurative sense is from an ancient anecdote that describes how planting either the peach or the plum tree in spring will give you shade in summer and fruit ripe for the picking in autumn as opposed to planting, let's say, thorns; also refers to the fact that peach and plum trees take considerable amount of time and care to cultivate, but the fruit is always sweet.

Noun

 * 1)  peaches and plums
 * 2)  peach flowers and plum flowers
 * 3)  all the pupils of a teacher over their lifetime