Yes but don't leave them to long under 12/12 or you will have problems with hermorphindykes.
One of the best tools that I have found for sexing is a $10.00 hand held microscope from Radio Shack made by MICRONTA. You can see your plants sex organs long before you could with the necked eye. Plus any unwanted creatures you may have on your plants.
If you know where to look when your plants are about 20" tall then you don't have to 12/12 them to weed out the males. A good deal for 10 bucks.