Portia makes an excellent point about the triggers. Each in their individual ways provides a window into the things that are hard for these kiddos:
Perceived inconsistency in application of rules. Happens every day. Drives my son literally to distraction. Pings in the PG kid's need for justice and rationality.
Anything "boring" which likely means either (a) too easy and repetitive or (b) a challenge - which he is unused to facing. Pings in either (a) rapid acquisition of knowledge and desire to move on or (b) perfectionism and excruciating embarrassment at perceived imperfection.
Chaos and loud or unpredictable settings. Read that as "any public school classroom on any given day."
Smelly things. Read that as "lunch time in any public school cafeteria."
Things that don't make sense. Read that as any one of a million classroom rules, for example "only reading books at your assigned level." Or any one of the many inaccurate statements heard each day, including as made by teacher.
Uncomfortable things. Kids sitting too close at [the always horrible] circle time. Sand in shoes. Tags. Blisters. Leaf blowers outside the classroom. That kid over there making weird noises.
Disrupting things. Just getting to the exciting part of a story when reading time is OVER. Itches that can't be scratched, leaving behind towering frustration.
Isolating, lonely-making things. Feeling different when other kids want to talk about [typical kid stuff] and PG kid wants to talk about [seriously atypical stuff that other kids aren't interested in and teacher doesn't want to hear about/doesn't know about/suggests is wrong when it is NOT].
When I start listing all the things that can sincerely upset and distract a sensitive, intense kid - big surprise they are off kilter much of the day. Just one more thing to help me keep my patience!