The blast sent a plume of smoke above a busy part of Mogadishu during the morning rush hour and shredded part of the school.
Al-Shabab extremists have claimed responsibility for the deadly attack at Manda Bay Airfield early Sunday.
Gunfire continued into Wednesday morning, and dozens of trapped people were rescued overnight.
Reports that Iraqi Baathists, Iranian elements, and others have played a role in the workings of ISIS do not appear to be in keeping with the principle of ideological purity on which the Islamic State says it is based.
Why do thousands of people, especially young men, join or support violent organizations, especially those like ISIS -- and how do we stem this tide?
The bombing hit the center of the city of Mogadishu.