OK, I have same problem - it's a boy thing really and will improve. My ds was born Oct 95, same as yours I would think!
There are ways to deal with this, and to avoid in September what is known as Year 8 dip.
I check ds's contact book/homework diary/planner every evening when he gets in to see if there is any homework. If there is, he does it after having a drink and something to eat. My take is do it now, or Sunday, and he chooses to have the weekend free if possible. I make sure that there is clear space on the table for him to work, and have an unending supply of pens, pencils, rulers etc in my desk.
If a test is written down, then I make him revise.
We pack his bag in theory before he goes to bed, so it's less hassle in the morning. I also write in his book what homework is due to be set each day, and tell him to wrote none set when he's not given any. When I was teaching secondary, I got the my students to write down their h/w, then I walked around the class to check it had been written down.
Where has the level dropped from? If from primary school, then I wouldn't stress too much, as a level 5 at primary equates to a 3/4 at secondary. Parents always find this strange, as it isn't a straight continuum.
It's difficult to strike a balance between helping and hindering. I look at ds's homework sometimes and proof it for him, as that is quite a skill to acquire. If his h/w is one of the subjects I taught then I'll offer advice, but I get yelled at if I suggest another way of doing things. Sometimes they need to fail in order to learn, if you see what I mean.
The problem with year 7 is that if it's a state school, then kids come in with having done different things, and much of year 7 for some is boring as they have done all the work before. The problem is kicking them out of this inertia in year 8, otherwise they dip, especially boys, and go backwards.
It's fine to get them to revise for tests, but not otherwise necessary unless they have end of year exams. The subject matter changes in year 8, and although things may be referred back to, they won't get retaught until GCSE; in history for example, if they're doing 20th Century GCSE, they'll not look at the Tudors again.
The trick is to keep them enthused about school rather than put them off. I taught some boys in year 8 who were disorganised, scruffy work etc; I bought one of them a pencil case filled with biros, pencils, ruler etc each year, and checked he had it each time I saw him; but they had turned it around by year 10, and passed their GCSEs.
You can also go to the Standards Site: Schemes of Work, and that will tell you roughly what he should be studying this year for the National Curriculum.
Hope that helps. Just stay calm though and you'll get there. I got told yesterday that he waned help, but in a more constructive way than I was offering it, so that was something. I think he means 'how about this way?' as opposed to, 'No, that's wrong' (even when it is!)