In loco parentis means "in place of the parent." A person or legal entity, like a babysitter or a school district, is considered to be operating in loco parentis when undertaking the care and control of another person, usually a minor, in the absence of the natural parents and in the absence of formal legal approval.
Traditionally, in loco parentis involves a temporary delegation of parental power, not a permanent and involuntary derogation of parental liberty. During this time, the natural parent is free to limit the scope of power delegated, direct the actions of the temporary caretaker of the child, demand accountability from the temporary caretaker, and terminate the delegation of power.
This doctrine does not entail any power to override direction from a fit natural parent.
Contrast the proper exercise of this doctrine to the inappropriate behavior of certain school administrators, who override parents' written instruction on behalf of their children.