Spelling is important. In my trans-Atlantic household, with two breeds of newspaper, the crosswords can get very confusing. My personal bugbear though with differentiation in spelling between English-speaking countries? Microsoft and the default to US English feature.
More to the point, learning a rule of language or grammar at school is admirable - breaking it later will be all the more satisfying when you can explain exactly why you deemed it appropriate. Don't abuse the poetic license, he's a fragile little chap
