They were less likely to report having ever been taught in school about AIDS or HIV infection (74.6 percent versus 86.3 percent), the CDC found.
Overall, in 2011, 12.9 percent of all students in grades 9 through 12 reported that they had ever been tested for HIV, but the proportion reached 22.2 percent among those who reported being sexually active (49.2 percent of males and 45.6 percent of females).
In the older group – those 18 through 24 -- 34.5 percent reported ever having been tested for HIV.
The CDC has recommended for several years that HIV testing should be part of routine medical care, but Frieden said many doctors still haven't bought into the idea.
"You have a very, very small proportion of who refuse testing," he said, "but unfortunately a relatively large proportion of doctors who don't make it routine."