Dd1 (9) has been sent home with a spelling list that gives the plural of 'gateau' as 'gateaus'.
Being a clever-clogs know-all, she apparently informed the teacher that she'd looked it up in the dictionary, and the plural was actually 'gateaux'. Teacher maintains the normal spelling is the -s one, with the -x spelling as an unusual alternative. Dd1 is spitting tacks.
Who do you think is right? Your votes, please.