What is he doing to earn those behaviour detentions?
Most Year 9s are absolute twats. It's inherent in teenage DNA that all but the most perfect (who become twats at a later point, sometimes University) or the utter nightmares from Year 7 and 8, reach Peak Twatness in Year 9.
Usually, they begin to sort themselves out towards Christmas of Year 10, a few carry on until the start of Year 11 and suddenly realise 'shit! I've got GCSEs' and get on with being a reasonable human being. A very small minority carry on being twats in Year 11 and sort themselves out when they're doing resits at college instead.
To be honest, if his father isn't supportive, I'd not bother with him, as all he's doing is undermining you and the staff (are they largely female, by any chance?).
If there was an underlying cause (such as his father being a dick, friendship issues, etc), I'd want to find out, but it could be that he's got that hormone peak just as his mates are also like it, but he's the most obvious offender where they have the sense to not be so visibly twatty.
What's worked with a lot of kids is to ask them if it's really worth the effort to argue/answer back/talk when you've been told to work in silence, etc. It's just not worth it for a lot of them and they chill out a bit.