That is ridiculous. My GP also charges £10 for sick notes.
My friend whose DC gets recurrent throat infections has been asked to provide a sick note each time her DC is off ill - this is despite the fact that when he returns, he is on Antibiotics, and he is under ENT and on a waiting list for a tonsillectomy.
He isn't even off a huge amount - maybe 2-3 days every half term, he is sent back as soon as the AB's kick in and he is no longer in pain and can actually eat and drink again.
And yet I wasn't asked to provide a sick note at all, by the same school, when my DS1 was off for over half of the first half term this year, first because of erythromycin resistant strep throat, and then just two days after he went back to school with that, he came down with appendicitis and had to have his appendix removed.
It seems that in our school at least, these rules only apply to some parents.
My friend isn't very 'clued up' about proper procedures, and had no clue how to argue her case, so the power crazed HT tries to insist on the £10 a throw sick notes.
The HT knows, however, that my response would be that I would happily provide a sick note as long as they would meet any costs I incur.
As they aren't going to do that, they aren't going to get a sick note!
I didn't have to provide a sick note to them for over three weeks off school - they had one for the strep throat, but ONLY because I had one anyway because I had needed it in order that DS1 could sit the alternative sitting of the 11+. I wasn't even asked for one for the appendicitis.
I would ask to see a copy of the school's attendance policies, and see if they are sticking to the published information.
I would also inform the school that I would be willing to provide a sick note as long as they are willing to cover any costs incurred.
It's a ridiculous policy, and IMO only encourages people to send infectious DC's into school, making more DC's ill.
And illness is meant to be marked as Authorised Absence anyway. Did you ring the school to inform them of your DD's absence on the first morning she was ill? You should then follow that up in writing in a short note to the school.
The school should be expecting self-certification for at least the first 5 days of any given period of sickness. No different from an ordinary workplace.
It's a waste of a GP's time to be writing sick notes for short term illnesses too.