Yes - mummytime you are right - do keep a record, schools often try to make out they were unaware of the severity of problems . At my DD school all communication is by email (and they are not received, no record of reciving etc)
Does your son still have friends? Sometimes school can be very intimidating if your friend group dumps you. Your son may feel overwhelmed by the prospect of GCSE's and the work, expectations of him etc that lie ahead. My DD in year 10 is getting increasingly fed up with school - the noise, boring lessons, the exams, aggressive classmates and the prospect of only more and more of the same in the future.
Sorry I can't offer more practical suggestions. There is always the option of home edding or the EWO agreeing to let your son stay home and the LEA providing some tutoring online or in person as a last resort. There are lots of archived and active threads on MN about Home ed.
My friend has a "school refuser" DD who really hates the noise and chaos and school in general and has done for years. The secondary school have agreed to let her come in late, leave early go to the med room and call home etc when it is getting too much for her, hoping that things will improve.
She also sees an Ed Psych but she still hates school but does actually mostly attend.
I don't think punishing your son will help - you need to gain his confidence and get him to talk quietly and rationally either with you or another party - perhaps a school counsellor?
Good luck with it - its hard.