Sorry SusanC I tried to quote part of your post but it wouldn't let me.
I will put it simply then. Imagine that a husband and wife have separated. Then imagine the husband is aware of attempted suicide and heavy drinking. Husband is being denied contact, and there are no court orders in place. Maybe social services have been referred by the school. In such a scenario in the UK, the social worker would attempt to contact the father and request that he exercises his shared parental responsibility, and collects the girls from school, and takes them home with him in order to safeguard them. This is what happens sometimes. If the school were to ring me or a colleague to check if this was OK, we would say yes, unless the mother can show the school a court order preventing the father from exercising his PR.
Buy as you say, this is California. It may not be the same.
EDIT, meant to say, school could be substituted for home, or anywhere else, but the father may choose to stay away from the home unless accompanied by reliable professionals, and to provide the children with somewhere neutral.