Teacher Carolyn Foley sent a letter
to the parents of her students. It's worth reading in full. Here is a quote she includes which piggybacks nicely with what I said here
Don’t worry too much about technicalities and misspelling. (Some-times we over-stress spelling because it gives us something easy and clear cut to land on. We mustn’t overlook what is being said.) The school has primary responsibility here. Grammar can always be repaired if sincerity and interest are present. On the other hand no amount of “correctness” can cover up the empty world of a child who hasn’t been helped to get interested and excited about something, preferably many things.