I charge the same rate for different ages but I charge differently based on hours of care needed.
My state assistant program though pays a different amount ofr each age group with infants (up to 1 yr) having the highest rate and toddlers next, follwed by prechoolers and SA'ers gettting the lowest rate payable.
If I HAD to do it on a scale based on age, I would do it the exact opposite because the littles don't break things and go through massive amounts of craft supplies and toiletries.....plus the littles only cry not sass....
