I have tried to keep this condensed for the sanity of all reading, sorry it's still quite long.
My DSS is 13.5, but can easily pass for 16/17. He can be charming, funny and a pleasure to be with.
However he takes no responsibility for his own actions and we are truly at a loss as to how to get it through.
He has been a handful since I first met him at 5. Until a couple of years ago he stayed with us every weekend/school holidays and spoke to my DH daily by phone. Over the years there have been behavioural issues (disruption/bullying/defiance) severe enough to warrant exclusions at primary school.
He never behaved that badly with us, but his mum always struggled to cope/discipline effectively and finally gave up 2 years ago- we got a call saying 'take him now'.
We involved mentors, had CAMHS check for ADHD (nope), and spent months fighting to get him a trial in a mainstream school following referral to a PRU. After 18 months of lies, stress, being excluded from school several times and a pregnancy scare with his 14yo gf, the last straw was him contracting a nasty STI and being referred to SS. He returned to his mother in April with promises of a fresh start. By this point we were both on the edge of sanity so tbh it was a sad but blessed relief.
Fast forward 12 weeks. Within a month of leaving us he was kicked out of the new school and back to the PRU. He'd been skipping school, swearing at staff etc. and they categorically will not have him back.
His mum threw him out after discovering he had emptied her bank account. He'd spent @£1500, mainly on trainers, clothes and mobiles. His reasoning was that she was being mean with her money, and that it was her fault for letting him know her PIN number. He'd also been smoking/selling dope and bought a moped at some point 

So he's back with us.
We've muddled through the summer- SS refuse to take him into foster care 'as he has a stable family home'. The fact that the other 4 people in the house are at breaking point doesn't matter apparently 
The relationship with his mum is so volatile that it has been agreed with all parties and his SW that he has no direct contact with her for now.
She has sought solace in the church, and has tried to get him involved. He has gone several times, but usually used it as an excuse to detour elsewhere when he was grounded. He has no genuine interest and laughs at her behind her back.
He's been back at the PRU for 3 weeks. We'd bought more clothes- uniform policy has been relaxed a bit says DSS. Got a call on Friday saying he has been told constantly about wearing wrong tops. Money wasted.
Got a letter last night saying no dinner money paid yet plus arrears from when he was with his mum. He has been leaving the house daily with £2.50 to pay for a £1.85 meal so DH has hit the roof. Excuse was 'they didn't ask me for the money'.
Confiscated his mobile and cut up SIM card.
Spoke to his mum this morning and he text her AFTER that so he has another phone hidden somewhere. Said he wanted to be baptised, we're guessing he's trying to get back into her good books so he can move in there again.
He left this morning wearing a coat I've never seen. When I asked where it was from, the story (involving his mum) didn't ring true. Sure enough, when DH asked her, she knows nothing of it.
DH has called SW and stated he can't cope any more and wants him out. I have battled through this with him and I can't disagree. Everyone in RL who has watched this unfold is amazed we have got this far without killing either him or ourselves 
Having read back what I have written, I feel so sad. He seems determined to throw his life away and we are powerless to stop him.
Any advice will be gratefully received. I am going to work shortly so if I don't come back before this evening, I haven't dumped and run, nor am I a troll 