The curriculum is designed to work very well for 3, 4 and 5 year olds. Children understand things and internalize things in different ways based on their age and maturity level, but most children in this age bracket will enjoy most activities suggested in the lesson plans. You can simplify activities for certain children and make them more intense for other children who need more of a challenge. Most Joy Schools have mixed classes of 3, 4 and 5 year olds and find that this works very well as children learn to help each other and follow the example of the older children in their group. Parents of very precocious 2½-year-olds have found that their children are ready to start, however, being potty trained is a definite prerequisite.
Really, each age has its advantages and delights when teaching. Some parents report that they simply love teaching a wide-eyed group of two years, while other parents appreciate the attentiveness and “really getting it” aspect of teaching five year olds. And who can dispute the fun of teaching a totally immersed group of three and four year olds with all of their comments and perceived drama? Probably the best advice is just to try not to have too diverse of a group age wise: not only does it make it easier to gear your lessons towards a specific age group, but it also creates a group that can “grow” through Joy School, doing two or three years together before starting kindergarten.