You're going to have to specify what you mean by "unions" being the problem.
Easy. You need a way to get rid of bad teachers. This should be obvious. Unions in many states have made that extremely difficult. Unions are there for the teachers, not for the kids.
Define "Bad Teacher". I pose that any definition you can come up with I can counter a set of circumstances that change that teacher to a "Good Teacher". Now here's a question: why would any intelligent person want to become a teacher? They are going to be evaluated on metrics that are a lot of the time outside of their control. They have to deal with curriculum that is wrong(think Texas). They don't have the support of parents. They have class sizes of 30+ in the good districts (have you ever babysat more that 5 children at a time before?). i think all these problems go away if the children aren't guaranteed a spot in the class, they have to work for it. Put in place a process where the teacher can have the student removed from the class. This allows teachers to have the leverage they need to change all of the above problems. But what do we do with the children who where removed? Let them know it is a privilege to be in those classes not a right and say better luck next time.
Active directory is not only used to authenticate users, where it's value is derived from is the ability to organized your entire computer network into organizational units and apply custom policies to each of those OUs. Think of this as having a *nix repository for every OU and in this repo there is a custom script to modify