If the minor was not in custody, it is perfectly legal for the police to question them without their parent(s) present.  This typically happens when an officer has a reasonable belief that a minor has violated the law.  In that instance, the officer can detain the minor to conduct an investigation and during this initial detention, police are not required to let a minor call his parents.   If the minor is in custody, they have the right to call their parents and have their parents present during questioning.  Custody typically means arrest but if a child is questioned at school it has successfully been argued that this too can constitute custody.  Essentially anytime that the minor's Miranda rights are implicated they have a right to speak with their parents and have them present.Note:  And as with anyone, regardless of age, if in custody and not given the Miranda warning no statements made by them can be used later.  However, prior to being placed in custody, any statements made can be used against them, or if they were read their rights and made voluntary statements after, those statements can also be used against them.