I had typed this out in more detail and lost it when I recieved a call so you will be spared my normall verbosity. First my post we neithe anti mom nor anti teacher. Mearly anti social engineering.

The problem with two fit parents is that an attempt to pick who is most fit would not only impossible but expensive and destructive to what little realtionship is left between the parents or even the kids. The path of least damage is often to go with the mom as default and move forward from there. Fair or not that is the reality of the world we live. If you really want to llmit the damage make divorce harder to get stop treating the noncustoial parent like criminal in the name of the children. Way have made divore a viable option to people who decide they want a new life.