Is the child in your care already as in just going to school for the afternoon. In that case I would continue to charge the parent the full day rate in the sense that using the time usage equation you start just after 12 to do diapers, dress, walk to the school and then walk back so the time you are "directly busy" because of the chid is till you get back from the school even though the child isn't with you. The two hours the child is gone is the same two hours the others are napping. Child is eating lunch and snack and doing the morning crafts that cost money so they are using the bulk of the pay for the day so a good argument for charging the full rate.