This 100%. You can still go to parties, go out, meet people etc. and still do well (though not in exam weeks)
Even if you forget about simple fun and enjoying yourself though and the only thing you care about is marks, its still good to have friends. Me and one of my mates shared EVERYTHING in year 12, even our essays before assessments and stuff because we knew that the other guy wouldn't copy it. I'll be honest, I would not be where I am now without his help and I reckon he'd say the same thing.