I don't know who decides the age-guidelines on films and dvds. But I find it best to ignore them... Last night we were all watching Braveheart. My boys (11, 8 and 7) love it - even though it's a 15. They'll love the new Robin Hood film as well - and I'll let them see it once it comes out on DVD. Why would it be unsuitable? Violence? Swearing? Nudity? They already live in the real world - where violence is a natural human way of being that we learn to control rather than deny. Swearing? Playgrounds are full of it - and kids learn where it is acceptable/unacceptable. Nudity? Bad scenes are rare in the films we watch. I sometimes skip a scene, but for the most part, they are not interested and barely notice. When you look at the way sex is used in 'acceptable' marketing, they're already over exposed to it all anyway. Honestly, my kids get nightmares from Dr Who - and Roly Mo (a cuddly reading mole) of a kids programme. Never from dvds we watch together. I would have thought that if we watch a dvd together, we get to help them interpret whatever they watch. Much healthier than allowing some unknown boffins to decide what's suitable for them to watch?
I've also used the ratings as a guideline and used a bit of common sense. That's all very well until your kids are older and reach the sleepover stage. Away from home, they get to watch films that you may not particularly want them to see but you have no control over. My daughter's been well and truly scared in the past watching films that were inappropriate for her age - but she'd never admit it now!