Can my pay be reduced, when I was given the position and not informed I was required to have additional college units?

I am employed as a teacher at a private church/school and have been for several years. Two weeks ago, I was informed by my supervisor that I do not possess the required college units to maintain my position and until I do, I would be demoted to assistant teacher but with no reduction in pay. This is the first time I was told a specific number of units were required beyond what I currently possess. Today, I received a memo from my supervisor, which says, if I don't possess or show proof of enrollment by July 1st, to obtain the additional units, my pay will be reduced to the position I was demoted to. Had I been told the requirements up front, I would have enrolled in college classes long ago and have the units needed. None of this has been part of a disciplinary process nor is there a reduction of force in place. I don't have an issue obtaining the units but what if I'm unable to do it within the prescribed time frame? Thank you.