Dd (year 10) is in the choir at her school. It's an independent school and they take the choir very seriously. She has recently been ill and missed ten days of school so four rehearsals for the end of year concert. She went today and all was well, she knows the pieces as they've been singing them all year. The music director has just sent an email saying she isn't allowed to sing at the e d of term concert as she's missed some rehearsals. Dd is in bits 
I'm not an "emailer" and I'm usually happy for the school to do whatever it thinks is right in most situations. But dd loves the choir and is really committed to it. She swears there is nothing new and she's sung these pieces all year.
Shall I email? If so can you help me with what to write as I'm hopeless at confrontation 