All schools are at different developmental levels of their program, but as a rule of thumb, three years. (magnetschools.info)
How might goal - setting practices vary for individual students at different developmental levels? (ascd.org)
One of the challenges of adopting a toddler or older child from foster care or international adoption is that you are actually adopting and ultimately parenting many different kids at different developmental levels all in the same child. (creatingafamily.org)