Our heroine is "number 83," aka "Megan Walsh" - played by Hailee Steinfeld. She's been raised all her life as a assassin, and she's very good at it, but what she really wants is to be a normal teenager. After a mostly successful mission, she has the opportunity to let her handlers think she's dead - which she does. And off she goes to high school.
From there we get a low grade high school comedy with lots of movie references: Megan has seen "Mean Girls," "The Breakfast Club," and plenty of others, but doesn't really understand high school - or even normal people. Just as she's starting to figure out where she fits, her old life comes back to haunt her.
Predictable and low on laughs. They set up a sequel, but not only is this movie's Rotten Tomatoes score 26%, its worldwide box office take - as of 2020 - was slightly under $1,000,000. I don't know the original budget, but I suspect it was a bit more than that - and return-on-investment is the only decider that matters on making sequels.