My husband plays rugby. He trains twice a week and plays a full match every saturday. Every week he comes home literally covered in contusions, cuts and scrapes. In the four years we've been married, he's had three trips to the hospital: broken arm, and gashes to his head requiring stiches (twice). He also had metal pins in his wrist and a permanently damaged ring finger on his left hand from previous injuries. And this is a man who boasts that he's never had a 'serious' injury!! One of the guys on another local team received a severe neck injury quite recently, and will probably never walk again.
It's dangerous. There's no getting around it. I do not enjoy seeing my husband come home every week looking like he's been in a war. However, I do believe that it can be a very positive influence in a boy's life. My husband thanks rugby for giving him discipline, keeping him fit, and keeping him away from drugs at a time of his life when alot of his friends were bored and experimenting. Even now that he's playing a little less seriously, it still does him a world of good - he's very fit, he gets to see his mates every week, and I honestly believe it is a brilliant outlet for aggression - a milder and gentler group of men you will not find!
A good rugby coach will train the young lads how to safely take impact, how to fall, etc to reduce the risk of injury. But there's always a chance, I'm afraid.