Class that might cause some high schoolers to blush

HEALTH

This subject often covers topics like nutrition and human development, including lessons that might feel awkward for teens.

This clue plays on the idea that "Health" class in high school often covers topics like puberty, relationships, or sex education—subjects that can make teens feel awkward or embarrassed, hence "blush." The word "class" is a direct hint at a school subject, while "high schoolers" narrows it down to a course typically taken during those years. The answer is straightforward once you connect the discomfort with the usual curriculum of Health class.