You are legally not able to retaliate against someone for this type of scenario as you are a witness to an illegal activity that was performed by the school. Under federal law that is a protected activity. Evidence can be shown if they do fail that they are being treated unfairly, as others students grades can be subpoenaed by a court to prove that they are being unfairly discriminated against. However, they are allowed to fail the whole class and that would be entirely legal as one person is not being singled out. The repercussions of that would possibly be reassignment or loss of employment depending on tenure. If they do fail the whole class: the school can scale the grades, as it would look bad on them if a class fails. Also, if an entire class fails - then the media would see that and it would make the school look bad, which could possibly effect local funding for them. Moral of the story: don't do something that is unconstitutional or you're going to have a bad time.

See reference for the information regarding protected activities: https://www.employmentlawfirms.com/resources/employment/how-prove-workplace-retaliation.htm

I am not a lawyer