If teaching was really 8-4 with 12 weeks holiday we'd all be doing it. But its not. I am the parent of a special needs child and I know how much extra time our classroom teacher puts in to just my child. Let alone the 28 others in the class.
I'm pretty sure the classroom teacher will find the time to reshedule your childs news OP. Funnily enough - they realise these things are important to a child.