I was lucky, my mother taught me to read when I was 3 and by the time I entered kindergarten, I was reading and printing. My teacher was great. She let me help make the snacks and let me read to the class at storytime. Other teachers just told me to grab a book quietly when I finished my work ahead of the class or took an extra 2 minutes to copy some extra sheets of something for me. Seriously, it wasn’t an inordinate amount of work.
Needless to say, after my experience, I was astounded by my son’s teacher! Most decent teachers I know, actually all the decent teachers I know are delighted when they encounter a bright child with involved parents.
I’m glad your mother didn’t listen to them. :)