The line will be fairly clear when they do fight together. Istredd's control can be sensed and Lucifer knows him well, he'd be able to tell if something seemed off. Instead he'll be able to let loose a little. Maybe that is what he's needed all along, an outlet for the ugly cracks inside. He needed to be open to it though.

I am going to go with ... very likely they can, yes. But the people who have access would be watched closely. It's a serious job, being the head of each of the schools. Since the men and women are separated. Then again if Stregobor could, I feel like he likely would. I don't know the spell myself. Stregobor may not see these students as enough magic for him to care about. He is a deeply selfish person, masquerading as a community leader.

Grace is what makes you an angel, right? Your essence.