la menor
A guy's face when he sees a tiny girl with a big body, thinking she's a woman, but she's still a kid. She's probably still in elementary school.
I saw la menor at the park. She was wearing a skirt and a bra, but she was still in 4th grade.
My cousin saw la menor and thought she was 18. She was still in 1st grade.
That girl at the store was la menor. She looked like a woman, but she was still in 6th grade.