My youngest is in year 6 - the last 2 years have been horrendous and I believe mostly due to hormones. (She’s always been a little bit of an outsider but happy and confident with it until 2 years ago) her mood swings were terrible, the emotional outbursts, crying for seemingly no reason, not wanting to go to school, arguing with her older sibling, became very avoidant and would hide away in her room the whole day if she could. Very disengaged. She really lost her confidence and would come home nearly every day upset and saying that no one likes her, she has no friends, she’s useless at everything… it’s been heartbreaking
the school recently ran a SHINE programme which may have helped (she’s recently turned a corner and we have our ‘normal’ happy child back so I’m guessing the programme helped some, but she did also start her periods a few months back so this may have also calmed her hormones now?) and she’s had some support sessions with a teaching assistant that helps with emotional support.
There are some apps we tried that might help you - child friendly mindfulness ones, meditation and yoga, breathing and grounding techniques. Check with your local council - ours have online group classes for parents
might not be relevant, but a new teacher a year ago also queried if there’s any autism/adhd going on and we are now a year in to the 3yr waiting list for assessment, this was due to her being withdrawn and easily upset at school (sitting quietly looking sad, not really engaging with others, rather than any disruptive behaviour although her attention span has always been pretty non existent)
as for the SATS, I’ve always just encouraged mine to do their best, practice when they can, but that I’d be proud no matter how they do. I don’t like exams anyway, I’d have a panic attack and go blank for every single one, but would only pass subjects because my coursework mark would carry me through. I find it a little cruel the pressure that’s put on children about exams.
good luck and I hope he settles for you soon