We need to see the head. Why? Because at 5 weeks, the cockerels begin to sprout red combs and wattles. The pullets will have no wattles and yellow combs.
Cockerels will also grow their tails much slower than the pullets. Early, long tail feathers is a pullet sign. This stuff isn't 100% but very, very consistent.
Click on this photo. You'll see my bunch at 7 weeks. Can you see how obvious the cockerels are? They are the ones with red combs. The pullets still show nothing. Yellowish tiny combs and no wattles.