A few times in the past I have posted about the success of using a "Upset because/You can help me by" set up on a communication device, book or in a separate binder.
(Link to the first post and the second.)
The "Upset because/You can help me by" framework was something the SLP and I created at my old job to assist a student and have since used with many, many students. The general principal is that when a student with communication challenges becomes upset (angry, sad, irritated, frustrated or any other version of upset) a staff member cues the individual to use the framework to identify the feeling, the cause of the feeling ("I don't know why" and "I am a teenager!" are both acceptable) and how a staff member can assist in easing the situation.
Currently this framework is being used in my classroom, yet again, with a student to ease in periodic distress. This morning myself and the other adults in the room were quite convinced of the power of this method when an AAC user, whom was just introduced to a page set using this method, was able to go from vocalizing in distress to communicating "sadness" because of a "schedule change" and requesting "explaination". Once the staff member responsible for the confusion (that would be me, oops) apologized and promised to make sure to communicate better next time the student pressed, "Sweet!"
The power of simple communication never fails to blow my mind.
All behavior is communication.