SAND SPRINGS, Oklahoma - Classes are canceled again Wednesday for a Sand Springs School after a carbon monoxide leak made dozens of students sick. About 1,200 students grades in sixth through eighth grades  are out of class. 

Staff evacuated Clyde Boyd Middle School and the Sixth Grade Center on Monday after students complained of headaches and dizziness.

Local hospitals treated more than 50 students, and two were kept overnight for oxygen therapy. The school didn't have carbon monoxide detectors at the time which the district says it'll resolve.

It's also replacing the malfunctioning heater which caused the gas leak. That heater will not be replaced Wednesday, but they can still have class without that one unit.

Superintendent of Schools Sherry Durkee is expected to update the media Wednesday about how things are going. They are waiting on the final approval to resume classes, according to Sand Springs Public Schools.

She said they won't have to make up the days even if they have to take three days off.