Hi OP, I work in exclusions as part of my job so might be able to give you some helpful practical advice.
Lots of schools do have ‘zero tolerance’ to drugs in their behaviour policies but there is DfE guidance on drugs DfE drugs advice that states that “exclusion should not be the automatic response to a drug incident”
I’ve clerked two panels recently where governors overturned PX for drug possession for pupils with no prior history of poor behaviour. The PX were overturned essentially because the school had gone ‘drugs = automatic exclusion’ and hadn’t considered any alternatives such as a managed move, and the school hadn’t provided sufficient evidence to show that the detriment to the pupil in being excluded outweighed the detriment to the school community in said child being reinstated. That’s vastly simplifying it but gives you the general gist.
I’d suggest talking to school and asking them for a managed move. If your son keeps his head down, behaves at the new school the managed move can become permanent. Schools often work together in geographical areas and have sharing panels where schools in that area organise managed moves between themselves. This might limit the number of potential schools available but is probably the best chance of securing a managed move.
If a managed move is not possible and the case goes to PX there will be a governor review meeting / hearing. You should attend this with your son and give as much information as you can in support of your son. It can sometimes be very helpful if governors see genuine remorse from the pupil. It can also be helpful if governors see your acknowledgment of the severity of your son’s behaviour.
At the meeting you will be able to ask questions of the school. Some things I would consider asking:
Why was a MM not considered (if they point blank refused one and went straight to PX)?
Why was permanent exclusion considered the most appropriate sanction and why does the school have a zero tolerance to drugs policy when DfE advice is not to automatically exclude for drugs incidents?
What advice and information has the school previously given to pupils on the dangers of illegal drugs?
Where / Who could my son have turned to if he had wanted to own up to having drugs in school? How is this communicated to pupils, ought my son to have reasonably known this?
It might be that the school an provide perfectly reasonable and justifiable answers but they might not. And even if they do it will help governors to consider whether the school might have been a bit ‘trigger happy’ in going straight to PX which is probably your best chance of getting the PX overturned.
The DfE exclusions guidance is also well worth reading.