I would love it if schools had a "time out" room. Students (and grown ups) with ADHD often have explosive anger or uncontrollable crying when highly upset. While they cannot control that, they CAN control how they react. The more self aware students have learned to remove themselves from a potentially explosive situation, sometimes by simply walking out of class. While this might seem to be insubordination, I would rather see a student walk out of class and possibly get into a little trouble than remain and get into BIG trouble. It reflects that the student is acknowledging that she cannot control her emotions at that moment but is being responsible enough to leave while she can still control her actions.
Usually, students who do leave go to student services or a trusted teacher's classroom, or even the AP office. A time out room, with guidelines in place to prevent abuse, would allow agitated students a designated place to go to cool off. The potential for abuse and staffing are two major issues, however.
Another issue is that it is so difficult for someone who doesn't have ADHD to understand how it is to have it. I was more empathetic than the average teacher before treatment, but I didn't understand JUST how hard it is to function with ADHD until I began the Strattera and started functioning more typically. I now have tremendous empathy and understanding for my ADHD students. But I wouldn't if I hadn't been diagnosed.
We all need a time out sometimes. One of the more important lessons of my adult life is the need to walk away at times from situations to defuse rather than remain and escalate.