What about religious preferences?

This is a difficult area for any judge, since the United States Constitution prevents interference with a person’s choice of religion. If a couple has an interfaith marriage, judges will generally look at how the children were raised before the divorce action was started.

For example:
The mother is Jewish and the father is Christian, but they had agreed to raise the children as Jewish and had taken steps in that direction, such as sending the children to Hebrew school and celebrating Jewish holidays in the home. The judge can more easily take this into account and make a decision if favor for the mother. If the father agrees, however, to continue the children’s Jewish education and not try to convert them or ignore their Jewish heritage, religion will play less of a deciding factor.

In some cases, the divorce itself may be initiated because of religious differences. Say, for example, that a couple was married in a Protestant ceremony and had always maintained a Protestant home until the husband converted to a small fundamentalist sect whose beliefs were anathema to the wife, and these beliefs lead to a divorce. The judge may need to consider the beliefs of the husband when deciding which parent will provide the best continuity and stability in the life of the children.

In a few rare cases, the judge will consider the religious beliefs of a parent, if those beliefs would endanger the health or welfare of the children. (Essentially, this is just another facet of the "best interests of the child" standard.) If, for example, a child suffers from a rare bone disorder that requires regular drug treatment and transfusions, and the mother belongs to a religious sect that absolutely forbids this sort of medical treatment for any reason, a judge would consider awarding the children to the father since the child’s life would be endangered without these medical treatments.

Some states and some judges will consider religious beliefs if those beliefs would interfere with the rights of the non-custodial parent to visit or be involved in the life of the children. If the mother, for example, belongs to a sect that states that children raised in that sect should have no contact with non-believers, including non-believing parents, until the children have reached the age of fourteen, this could prevent the father from participating in the life of his children for several years. The decision may be obvious, but still, the judge would be very careful in his deliberations concerning religion, even in this scenario.