In this special school, Lisa Elder doesn't have a lesson plan or an attendance book. She does have her walkie-talkie(对讲机). When the hallways are secure and the teachers ready, the call comes over the radio: Students are on their way up.

    Three teens, two boys and one girl, entered Elder's classroom. "Why don't you guys have a seat and I'll tell you what we're doing, "she tells them.

    Today, they're going to cut out leaves from construction paper and write life skills on them:

    "Patience. ""Hygiene(卫生)."

    Then, Lisa notices a boy named Brandon. He's hunched(躬身)over his desk and he's got his fist against his chest-it's shaking. Lisa tries talking to him but gets no response.

    It doesn't look like anything to me: just a boy who's not participating in class. But Elder has seen this behavior in his file, and she knows it's a warning sign.

    She radios for backup:" Could I have a youth worker up in life skills?"

    By the time the youth worker comes in, Brandon has turned his desk to face the back wall,   and he's getting more and moreagitated. He's still not responding.

    "OK," she tells him. "Here are the choices: If you want to stay in my classroom and participate, I would love you to. I will do anything I can to help you. But if all you're going to do is turn your back and avoid everything people are asking of you, then I'm going to have you brought down to the office."

    She pauses for a moment. "I would like you to make the better choice and stay with me."

    That's not the choice Brandon makes. It's becoming clear: He could lose control at any moment.

    Elder leaves the room, 20 minutes before class is over. As we walk down to the residential unit, she tells me, "So when I tell you that I don't know what the day is going to bring, that's a perfect example."