I do on occasion chair PEX panels. The guidance we all have to follow can be found at assets.publishing.service.gov.uk/media/64ef773513ae1500116e30db/Suspension_and_permanent_exclusion_guidance_september_23.pdf
This details what factors schools need to consider when looking at permanent exclusion, along with what governors need to consider at panel.
With persistent disruptive behaviour, schools are expected to have detailed notes on what behaviour contributed to the decision, along with details of what behaviour management has been tried, how effective it was, whether they have considered any Sen assessment, whether they have consulted with external support eg local authority behaviour team or academy trust. There needs to be evidence that parents have been included in these discussions.
These are the kind of questions you can ask at the panel. You can ask the school leadership and there should also be someone from your local authority "fair access" or similar - their job is to ensure schools are following the guidance appropriately and can advise on what options may have been available to school.
Sometimes it is hard to get to the bottom of a change in behaviour, and some time in a APC which is staffed with people who can help with this may be a good thing. Managed moves could help, but if the root cause of the issue is not identified, often the pattern repeats. You can ask school if a managed move was considered and if not, why not.
I hope it goes well and whatever the outcome, it is the right one for your family.