In our work with educators we call this the resilience window. One way to look at it is the space between your current stress level and your "lose it line"... when you flip your lid. We encounter many things throughout the day that raise our stress level and therefore shrink the "resilience window." As educators that might be a student who is not following directions, or bothering others. It might be missing lunch. As a student it might be a comment made by a friend, being frustrated academically, not having a friend at lunch, - and there are systems things that shrink resilience windows too. Things like: lack of clear expectations, lack of routines, systems of rewards, the practice of teaching by shaming, sarcasm etc. To me a trauma informed school is always looking to open the resilience window - for everyone. System changes include: using encouragement instead of praise, solutions instead of consequences, regular routines, SEL skill building, growing student voice through class meetings etc.
I attached a short piece from our administrators' guide on the resilience window.