Thanks all for the solidarity 
Cathster
Sorry you are also struggling to get your DD's school to recognise her difficulties. So hard isn't it, and a weird feeling to almost hope they will fall apart in school so that the teacher gets it 
Like your DD, my DS can't really articulate exactly what it is, although we gently ask him, and he does sometimes try... I'm hoping that might improve with time/age. And yes, it is awful to hear him say that he hates himself
Sadly we have almost got used to it, in that it doesn't surprise us any more because he's been saying it so regularly for so long (he also says he's stupid a lot, which is not true because he's extremely bright, but I think it's because he feels stupid sometimes). However, it doesn't hurt any less and the longer it goes on, the more of a worry, because we can't just put it down to a phase.
The SENDCo has referred DS to a external organisation that comes into school to do child therapy sessions so we'll see if that helps at all, it will be interesting to see if he feels safe enough with the therapist to open up, if they can shed any extra light on what's going on and help in any way it will be a bonus. Glad school can offer that at least, it's better than nothing.
Jules912
Really sorry to hear that your DD is struggling so much, and that the school are putting her isolation, that's sad. What kind of behaviours are they? Have you had meetings with the SENDCo and is there some kind of plan?
LightTripper
Thank you for sharing those videos, v interesting stuff and I agree with your take on the general trend with mums' v dads' approaches. It's certainly true for us.
dimples
Thanks, I might have to resort to filming him
during a meltdown, but I think I might struggle since I'm always so focused on trying to manage it - and he generally hates being photographed and filmed so there's a risk he'd kick off even more... I'll see what DH thinks and whether he has any ideas about how to do it subtly.
About your DS's therapy session, bit weird to say this as it's not exactly good when behaviour like that happens, but I'm glad the therapist saw it and hopefully has more insight into your challenges now. Also I wonder if it's a sign that he's "relaxing" more about the sessions in that he is not holding back?! Please do correct me if I'm wrong, I'm just wondering "out loud" really.
SusiePevensie
Am I right in thinking that it's less common for children to be ok at home and not at school? Although actually on reflection if there are fewer demands at home, there'd be less to trigger challenging behaviour, whereas school is more stressful for so many reasons.. so it makes sense too. How old is your DS?