Legal Question in Family Law in Massachusetts

If the Mother and Father are married or living together, which it sounds like they are in your case, then there is nothing that the Mother can do legally as long as the family remains intact. If the Mother plans to stay married or living together with the Father, then I would suggest counseling. If the Mother is considering a divorce or separation (if unmarried), then the court can address legal custody, which determines whether the parents should jointly decide matters about the children's education, medical needs, and RELIGION, or whether one parent should make those decisions (if the other parent does not appear to be able to make decisions in the children's best interests). Even if the court orders shared legal custody, if the parents disagree on a particular issue, (such as religion, as in your case), the issue can be brought to the court for a decision and order.

I would just clarify that the father is not in any authority position above the mother. There is simply no legal means for a married or cohabiting (living in the same house) couple to stop the other from preaching religion to their children.