You could probably get away with either, but I'd lean towards "teaching me grammar," since grammar is itself a school subject. It's just like saying "teaching me math" or "teaching me English" or "teaching me history." [Contrast that with something like "teaching me about imaginary numbers" or "teaching me about comma splices" or "teaching me about the Civil War."]
Ashley Newman-Owens
GMAT Instructor
Veritas Prep
Post helpful? Mosey your cursor on over to that Thank button and click, please! I will bake you an imaginary cake.
GMAT Instructor
Veritas Prep
Post helpful? Mosey your cursor on over to that Thank button and click, please! I will bake you an imaginary cake.
