Rules of the game?

When I was at school we played "rugger" ('cause we had pretensions to being a "posh" school), but we did at times play football, and my recollection is that we were taught that the only physical contact allowed above the waist was a shoulder to shoulder charge.  So why was Coloccini sent off in the Sunderland v Newcastle match at the weekend for shoulder-charging an opponent?  Have they changed the rules, or what?  And just to be clear - I have no interest in either team and thus no axe to grind.  Regular readers will know I support Wolves (Gawd 'elp me).