Most of the dead were students, the Syrian Observatory for Human Rights told Voice of America. The death toll is likely to rise, they said, because many of the injured were in critical condition.
Government planes have repeatedly attacked Raqqa since Syrian rebels overtook the town in March, Voice of America said.
Meanwhile, the human rights group said revels killed at least 19 government fighters during an assault on the Qalamoun area on the outskirts of Damascas overnight.
2014: The Year in Music [PHOTOS]