I had the same thing with my DD this year when she started prep as her name is Mayleaka but likes to be called May the teacher would ALWAYS write her name as MAY and even when Mayleaka was trying to write her name on her art work they would never help her out and just let her spelt it how ever she wanted without correcting her....

I have no advise though sorry but I do know how annoying it is when they cant get it right!!! and they are ment to be teachers....