Suppose that a teacher says
I will minus your points if you cheat.
To mean "I will deduct your points." Here, minus is apparently used as a verb. Checking out the dictionaries, it can be seen that minus is only listed as a preposition, adjective, and/or noun. However, some people argue that "minus your points" is a phrase commonly used. Therefore, I ask this question here to double-check that it is invalid to use "minus" as a verb.
Is this phrase acceptable? If so, is it commonly used?