This is a sort of AIBU I guess. I'm a governor at a school where the head has a poor grasp of punctuation, in particular the use of commas and apostrophes. So it isn't a one-off issue, or the odd typo. This week's examples include "the enjoyment of music in it's many forms" and "Please avoid disturbing the student's."
The school has a fabulous English department. Whilst the school has a lot of disadvantaged families, I'm fairly sure that the majority of the pupils could spot the errors. Personally I cringe when I read through the documents I'm sent and see the number of errors.
I feel incredibly petty raising it if no one else has. Equally I'm concerned that as the head is also determining the standards required from staff, then if their English isn't up to GCSE standard, there's a risk that their assessment of their colleagues might be questionable?