My daughter just turned four, and has long tangly hair... so it's gonna be a while before she can wash it on her own.

My son turns 6 in a few months, and has been washing and rinsing his hair by himself lately! The breakthrough was a swimming class he took... he got comfortable with going underwater, and that made bathtime sooo much easier. Wish we had started swimming lessons earlier, because bathtime was a nightmare for a few years there!