DETROIT — Michigan is catastrophically failing to provide many of the most vulnerable children in its care with a quality education, delaying some teenagers’ graduation by years or leaving them so frustrated that they drop out of school, according to foster youth, their advocates and educators who’ve tried to help them.  NBC News spoke with 10 current or former Michigan foster youth who collectively spent time in more than a dozen residential facilities in recent years, either because social workers couldn’t find a family to take them or because the state said they needed treatment for mental health or substance…