S.H.
She may not be constantly with your child at those times... BUT, she HAS TO, block off her time/schedule, per your daughter, everyday.
Because, even if your daughter is in school... she is still 'on-call'.... and has to be available for those hours, still. What if the school calls her and your child is sick or something, and the Nanny has to pick her up????
These things happens.
Thus, your Nanny is STILL, 'on-duty', for ALL of those hours. Whether or not your child is in school.
What if, you are not paying her for those hours your child is in school? And then the school calls you/the Nanny and says your child has to be picked up because she is sick or something. But the Nanny says "well I am not on-duty right now and am not on paid-time... so I cannot pick her up and watch your child."????
She is in her right, to turn you down. For these situations. Because, she would not be paid for it.... nor, 'reserving' this time slot, per your child's school schedule, to help you or your child.
AND, what if (and there usually is), times/events at school, in which the Nanny would need to be there? For field trips, or chaperoning something at school... .etc. This is COMMON, in Preschool. Parents, volunteer, or their Nanny.
IF you want your Nanny to do these things, she is STILL 'working' and for your child.
It is not just about being face-to-face with your child... but being 'Available" all the time, for all those hours, too... JUST for your child.
Regardless if your child is in school or not.
Thus, her pay, should STILL be the same.
I used to do childcare.
Whether or not the child was actually at my home, I STILL have to have those hours, SAVED for just that one child.... no matter what.
And I was paid, to do so.
No one said, you have to give her a pay-raise, every 2 months.
That is your choice.
Personally if someone docked my pay, for the reasoning you gave... I would leave, and find another family to do childcare for.
Doing childcare, is not 'maid service' either.