after 5 years IF the school board chooses to offer it. Tenure is not automatic. The employee is released if they do not qualify for tenure. It is not a god given right.
This does not apply just to College Professors.
IF a teacher does not perform, there is a well documented "due process" written into the Teacher's contract that allows for firing that employee.
The fact that lazy school administrators and school boards do not document problem teachers and remove them is not the fault of the 99% of teachers that do a great job.
Oh...and this is what is really behind all the teacher bashing in the media.