Watch with caution
Now I have put the rating at 9 and up because it realy depends on the child. I watched it aroound the age of I think 6 and I was fine with it.
This film is saying about Anakins descent to darkness, the fall of the jedi and the rise of the the sith and the empire. I won't say any more because I don't want to ruin anything.
Now first of all for the first hour or so it is ok there is actualy only 2 bits were there is death of a main charactor and that is oone of count doko which there is decapitation but you see no head or blood and then of general grevious where you do see a heart but only a glimps but that you will see is not bad. After that is does get very dark, and I mean very dark.
Order 66. The order to kill all the jedi and you see no blood but there is one sceen were anakin goes into the jedi temple and finds some childern and they ask what do we do, and anakin draws his lightsaber, and then you cut to something else, later you do see dead children with no cuts of any sort and one at one point that is fighting to let someone escape, he fights and fights but he has to die.
Now the battle of the heros is the next dark bit where obi won and anakin fight, and it is on a lava world, and near the lava anakin may lose his legs, and get burnt, and he does get a lot of fire damadge.
If you are looking to see if this is ok for your kid watch it yourself first then make a desision because as I said i watched this at a very young age and was fine.