I am a guy and my school K-12 was effectively the same group of people. There were very few new people each year, maybe one of two.
The movie Eighth Grade wasn't as funny as Ladybird, but I am also further removed from the subject. The dialog is spot on to what I remember. Apparently every um and ah is scripted but you wouldn't know that. Music is used magnificently throughout.
There are so many cringe worthy parts of awkwardness. I assume parents will view this differently than me. It looks like being a teen these days is so much harder than when I was.
All in all I liked it, but I can't relate to it well enough to love it.