The school are being dicks. The op needs not to be a bigger deck and go to war over this, especially if her dd is going to be new to the school.
Those shoes wouldn't have been allowed at my ds's school - primary or secondary.
Off topic, but why is your dd wearing boys' shoes?
DD was an H (sometimes slightly off the scale). I echo a previous poster and "German" feet German styles. However, in practical terms Start-rite used to come up wider than Clarks. Independent shoe shops do stock some Continental styles - Geox were brilliant for dd.
Alternatively, look at women's lace ups which come in wide fittings: Clarkes do some, New Look and M&S are options, so too might Docs be.
Will your dd want to wear boys' shoes at 12 when all the other girls are in unsuitable ballerina styles?
Don't be that parent op - not over a pair of shoes.
The older I get the more ridiculous I think school uniform is. Jeans, Jersey or sweatshirt, trainers just as in France- job done. French youngsters look so much better than ours in their I'll fitting polyester blazers, badly cut trousers and shirts, and all the girls here seem.to wear ankle socks with a too short skirt. It's a great look enhanced by regulation shoes.
It's a deeply British problem. If only schools focused as much on the quality of teaching which would be supported by more emphasis on improving behaviour and ensuring the experience of the many is not diluted by the behaviour of the few.