To only pay some of this "voluntary contribution"?

[sunshineandhappy]

Dd is in year 13, only 3 more weeks until her A levels start. Yesterday I receive a letter from school informing me that a guest speaker has been booked for this Thursday.
He will be giving a 4 hour compulsory tutorial, meaning the children will be missing other lessons, and staying behind for an hour and a half.
The sentence in the letter which has upset me is this ' should you feel able to make a contribution towards the visit, I would be grateful to receive a donation of £18.50'
AIBU to send a cheque for £10, stating that is all I can afford at such short notice?
Is school BU to ask for so much?

A voluntary contribution is just that. I am tired of them. I didn't pay one at all last term as I simply didn't have a spare ten pounds.

Its the school's job to educate your child, not provide business opportunities for private education providers.

Yes. And I'd not be sending anything.