And how did this manage to happen?

From the Daily News:

A teetering Bronx school construction site sparked the evacuation of neighboring homes and shut down two underground train lines during rush hour Thursday morning, officials said.

Firefighters sped to the Southern Blvd. address near Freeman St. in Foxhurst just after 6 a.m. amid concerns that the new school, which is under construction, was unstable.

The building’s braces appeared to be bowing, a source with knowledge of the incident said.

First responders evacuated nine neighboring buildings. About 40 residents had to leave, officials said.

Officials from the Department of Buildings said that while it did not appear that the building would collapse, more inspections were scheduled.