Vampire of Woodroffe High School (1975)

A student at Woodroffe High School in Ottawa unexpectedly turns into a bat and drinks another student's blood, killing him. The next time she transforms, her classmates catch on right before she takes out another student. They call the police as she hides in the school offices. They chase her down into the auditorium and stake her in bat form, causing her to revert to human form with vampire fangs and be stopped for good.