May I wade in here? (but haven't RTFT, so apologies if I'm repeating anyone else!)
The 9-1 GCSE English exams do assume that students are 'reading widely' - Depending on which board you are doing, the extracts for the fiction paper vary (e.g. an extract from a 19th century novel for Edexcel and a 20th or 21st century novel for AQA) and for the non-fiction paper (again, non-fiction extracts across 2 of the 3 centuries, depending on the exam board). And the non-fiction texts can be anything from a newspaper article about climate change to a historical document about workhouses from Victorian times!
And of course, all the Literature exams are now closed book, so the students need to know their set texts and poems very well indeed to perform well in the Lit exams. (Previous syllabus was doable at a push with reading the study guides!)
So all students from Year 7 onwards need to be reading often, and in Year 10/11 almost daily. It doesn't need to be for long - I recommend 15 minutes to my students - and it can be anything (as I think others have said).
OP, if I post the list of ideas I give all my new GCSE students, might that help your son? And anyone else with a reluctant reader either just starting in Year 10, or now in Year 11?
Here goes!
Suggestions which may to help develop more active reading habits, and widen experience, include:
Read a daily newspaper (hard copy, or online), or a particular
section of it that interests you
Read a magazine which relates to a subject, sport or hobby you
enjoy
Pick a 19th century novel from the school library (read the first 5
or 6 pages, then put it back)
Read another poem written by any one of the poets featured in
your anthology
Do some online reading/research about your favourite celebrity
or sports personality
Re-read your set texts - just a chapter/scene/poem a day from
each text in turn
Research the life of someone (contemporary or from history)
who is known for an extraordinary achievement.
Re-read a favourite book – or read a book someone else has
recommended to you
Read an unfamiliar text by a writer whose work you previously
enjoyed
If it's any consolation to anyone, when I do the tutor/student questionnaire with my new students (I tutor privately) I have a section which asks them about their current reading habits, and every single student I've ever had has circled the final option of "Only when I need to/when I'm asked to by school"!
With the previous exam syllabuses you could get away without reading anything much but this has all changed now.