PS The argument they had was due to a razor blade that went missing so whilts he was 'asleep' they searched his room.
My name is Suzie, online adviser at Family Rights Group. I am sorry that your post was not responded to sooner due to the volume of work we are currently.
You are clearly concerned about your son’s behaviour. Do you mean that your mum and partner has a special guardianship order? Am not sure what an SPO relates to.
It is not clear from your post how old your son is but if he continually fails to return home and put himself in danger then there may be concerns that he is beyond parental control.
As I am not sure what order your son is subject to it is difficult to give clear advice. It seems however that your mother and her partner are the people responsible for his care so I think you should allow them to deal with him. If not, your son will be getting mixed message about who is responsible for him.
If you can clarify the type of order and post again that would be helpful.