Facebook's losing its cool—again.

A report by Frank N. Magid Associates found only 88 percent of social media users in the U.S. between ages 13 and 17 use the social network, according to Bloomberg. That's a big drop from the 94 percent of users in the same age group last year. In 2012, some 95 percent of social media users in that age range were on Facebook.

A spokeswoman for Facebook declined to comment, Bloomberg said.

At the same time, usage on Twitter climbed 2 percentage points to 48 percent among users in the coveted teenage demographic, according to the report.

