@Daniel ****
as I told you, visas cannot be cancelled. But I doubt your wife is on a visa. She is likely on an extension.
The school cannot cancel her extension. They do not own her extension. Her extension is in HER passport and the only way to cancel the extension is with her passport and a letter from the employer stating the last day of work.
So when she goes to immigration to cancel her extension, you would also go and use the same paperwork as her to cancel yours in tandem.