A classroom has collapsed on pupils at Precious Talent School on Ngong Road in Nairobi County.
Several learners are feared dead in the the Monday morning tragedy, with Kenya Red Cross reporting that dozens trapped.
Four of the injured pupils have been rushed to Kenyatta National Hospital for emergency care.
The two-storey building in Ng'ando area caved in and came down a few minutes to 7am.
TV footage showed rescue teams from Kenya Red Cross, St John's Ambulance, school workers, residents and other Good Samaritans combing through the rubble and lifting blocks as they battled to save the trapped children.
Some of the rescuers used rudimentary tools, including sticks, to dig up the rubble as many parents watched in despair.
The school managers could not estimate the number of pupils who were in class when the building came tumbling down at 6.50am.
According to parents, the school managers called them immediately to notify them of the collapse.
The classes that collapsed were housing the junior primary pupils but the most affected are those in Standard Six, Seven and Eight on the ground floor, who were trapped in rubble.
Basic Education Principal Secretary Belio Kipsang is among the first senior government officials to arrive at the scene of desperation.
There were no fire engines on site and many used bare hands to save lives, bringing into question the city county's disaster preparedness.