UPDATE 12:45 pm

School officials in McKinney tell NBCDFW that police were called to the school at about 11am due to a bomb threat.  Students were evacuated and a sweep of the building was conducted.  No bomb or other devices were found.  Students have been allowed to return to class.
ORIGINAL POST:
WFAA-TV in Dallas is reporting that McKinnney High has been evacuated due to a bomb threat.  Students have been moved to a secure area.  No other details are available at this time.  We will continue to follow the story and bring you more developments as information becomes available.