Some advice please?

Is being called a leprechaun a racist comment?

I was was called today by an irrate parent to complain that their darling offsrping was called a leprechaun by one of our teachers and that 'was a racist slur'.

Now the remark could be offensive (could it?) but the child is NOT Irish, nor of irish decent-  but was wearing a green woolly hat.

(PS the family doesn't go caravaning - I checked. so  they shouldn't be reading this)