Fortunately this happened when no kids where in school:

A kindergarten building in southern Seoul has tilted after a retaining wall at a nearby construction site collapsed. No casualties were reported but the incident led to the evacuation of some 50 people at one point.
Our Bae Joo-yon has more.

Report: According to local authorities, the three-story Sangdo Kindergarten in the southern district of Dongjak tilted about ten degrees after the wall designed to prevent subsidence caved in at around 11:20 p.m. Thursday.

There were no casualties as the building was empty at the time but some 50 local residents had to evacuate and take shelter at a community center and hotel on Thursday night before returning home on Friday morning.   [KBS World Radio]

You can read more at the link.