All schools will have different systems but most GCSE students have English for 4-5 hours per week. So you'd be looking at at least 2 homeworks per week.
Also depends on the feedback policy - are some of them being peer or self assessed? We had a policy of teacher marking once every 3 lessons but had to revisit as it was simply unworkable - for me this meant 15 hours' marking per week, before I'd even started looking at lesson planning, revision sessions etc!
Many schools report to parents 3 times per year with a predicted grade for each subject and an effort grade. Individual subject test results will not be communicated centrally, you will probably need to speak with your child about these, ask to look at books, folders etc. When I'm feeling on top of things I tend to send reward postcards home if a student meets or exceeds their target grade in a class test, and many parents have come back to me and said 'I didn't know he/she was doing a test'. Teenagers eh?!
Hmmmm....not sure if that helps to answer your questions at all, but it might be that the teacher is new to the school / new to the spec / new to the marking policy?
It might also be that your child doesn't always hand their book in (there are certain students who can get through to January without me seeing their book because their automatic action at the end of the lesson is to scoop everything up and shove it in their bag). Does your son seem satisfied that his experience is typical of others in his year group?
Certainly raise your concerns but perhaps start with the class teacher. There could be a v simple explanation, or yes, it could need to be escalated.