Horizontal vs vertical tutoring: which is best?

I’d never heard of vertical tutoring until I started my job last year, and I thought it was totally nuts. Over a year later, I still think it’s pretty shitty, and the more time I spend with my bunch, I am craving the need to have horizontal tutor groups. 
My school has been battling for a few years to find the perfect way of doing tutor groups. In all honesty though, I’m still not sure we’ve found the right balance. 
I am a tutor of a mixed KS3 tutor group – meaning I have both Year 7s and 8s. I dislike it, I don’t agree with it, and my problem is the Year 8s. Having had this tutor group last year as well (and not particularly warming to them), I thought that once the previous Year 8s had moved into Year 9, and I inherited a whole load of fresh faced 7s – that my life would be easier. 
It’s not that easy though.
Year 8 to me, has always felt like a crappy year group – there’s nothing for the kids to do, they aren’t the youngest in the school anymore, and they’re not the oldest. They don’t do GCSEs or any other important exams, and there’s not really any key events for them to look forward to. As a result, I find that Year 8s can drift somewhat. 
The problem with this in a mixed tutor group, is that they become an issue for the new Year 7s. They are a bad influence. Suddenly, the Year 8 girls think they are the COOLEST kids in the school, and think it’s totally acceptable to have attitude and be an all round bitch, and the boys? They just can’t be bothered and have this weird sulk on most of the time. 
I want to smack the attitude right out of them. Obviously though, that isn’t allowed.
Anyway, as stated, my Year 8s are just a bunch of idiots, particularly two mouthy girls who DON’T SHUT UP. One of them, I’m pretty sure, is going to make me have a mental breakdown. 
My Year 7s on the other hand, are generally pretty nice. They’ve still got that Year 7, new glow about them, and they do sweet things like saying ‘Good Morning’ not ‘Yes Miss’. And I love that. 
But some of them are already picking up bad traits. Their shirts are untucked and their top buttons are sloppy. A few have even rolled up their shirt sleeves – obviously not realising they look like right twats! (It’s bad enough to see polo shirts rolled up in Summer term, let alone a stiff shirt!) 
Today one Year 7 shrugged off the fact that he’d been given an 80 minute detention (very serious) – in his FIRST week of school. What a knob! But what was even worse, was how the surrounding Year 8 students just laughed! 
I feel that if this situation had played out in a Year 7 tutor group – the rest of the class would have been so shocked, and scared that it might happen to them too, that no one would have breathed. Let alone found it funny. I almost felt like my Year 8s were encouraging his bad behaviour, because it gave them something to laugh about. Even after I shut down their stupidity, I could still see some of their disgustingly smug smirks. 
Currently, in my tutor sessions I feel that I’m drowning slightly, because I don’t know how to get through to those bad ones that their behaviour is wrong – because they don’t seem to care. I think a horizontal tutoring system would be better, there’s no one to impress and no one to encourage their bad behaviour. Plus, you get to know the whole group without having to get to know a strange mix of kids you know well and Year 7s you’ve never met. 
I was wondering if anyone else had experience of vertical tutoring and how they found it, because currently, it’s giving me a right old headache!