Definitive answer for sexing plants!

This is my first grow. I have 6 plants that are about 2 weeks away from the start of flowering. I have heard from some people that the sex of your plant can be determined by looking at the main stem of the plant where the arms, or petioles grow off. It it "Y"s at the stem than it is a male. If it is not at a "Y" and is unlevel on the main stem it is a female. Can any one prove or disprove this to me? Is unfair to assume that my plants are all male using this method?

No, my honest opinion..WAIT till your about 2-3wks into flower. There are signs, like the branching your talking about or males grow faster ect.. Wait it out.... It's not a definitive.

Ive never heard of that method. Best bet is wait till they preflower or once in flowering after a couple weeks they should be showing sex. Look for male pollen sacks or the female white hairs.