The Centers for Disease Control (CDC) recently released their Youth Risk Behavior Survey (YRBS) for 2019. It found that less than 40% of high school students in America reported having ever had sexual intercourse.
In 2019, 38.4% of high schoolers reported that they had ever had sex, down from 39.5% in 2017, 46% in 2009, and 54% in 1991. This slow but consistent drop in teenager sexual activity has led to decline of more than 15% since 1991. Further, while 38.4% of high school students reported having ever had sex, only 28.7% are currently sexually active.
To read more about this, check out this article from the Institute for Family Studies.