Kabul's Kaaj educational center was the location of Friday's suicide bombing that left 19 killed and more than 20 injured.
The official death toll is likely to rise, according to eyewitnesses.
The area in which the attack occurred has a majority population of Hazara, the ethnic minority group often targeted by the Islamic State.
Kabul police spokesperson Khalid Zadran confirmed the number of injuries amounting to 27 people, down after a revision of the 29 announced initially, adding that the blast occurred during the time when an entrance exam was being taken.
Schools and educational institutions are usually closed on Fridays in Afghanistan.
In the most recent months leading up to this attack, a string of attacks and bombs have targeted civilian areas, infrastructures, and even religious centers, most of which were claimed by IS-K.
Just in September, four people were killed and 10 injured after an explosion occurred near a Kabul mosque last week.
Another on September 2 left 18 dead after a major explosion rocked the Herat district's largest mosque, killing the mosque's imam.