I think you will gradually see that change. A lot of the fee schedules you see was when JK/SK was half day. Also they will not change the bus for you. You will need to walk the kids to the bus stop and meet them at the bus stop after school. I think up until the end of grade 1 they have to have an adult at the bus stop or they won't be let off. Which also means you may want to only take children that attend the same school as your own children or you could have conflicts in where you need to be for bus time. It won't be as bad for you if you are not also dragging younger children to the bus stop with you. Around me the going rates are $15 for either before or after and $25 a day for both. So it is about half the income you would make if you had younger children all day but cost wise the school kids will eat about twice what a toddler eats. Also the household deductions you can claim will be a lot less because it will be based on the hours the children are there which is closer to 4 hours whereas a full time toddler is in the house for up to 10 hours.
It is for sure something that you can do as long as you are not planning to use the income towards household expenses because you won't make enough to have much more than pocket money.