I was taught about significant digits in Junior High School science classes. (in a public school in US, late 1960s.) Answers were marked wrong if they had too many digits that weren't significant. Is this no longer taught in school?
Teachers have a lot less latitude nowadays; see [1] for an example that is shocking in the 1960s context.
1. https://www.cbc.ca/news/canada/edmonton/teacher-who-gave-zer...
Granted, the teacher that tried to teach me this had no understanding of it themselves and would incorrectly mark answers wrong when they had the correct number of significant digits, so it was pretty botched in my case. Still was attempted in the curriculum though.