First off, welcome to BYC
Now back to your question. There are many different ways to sex chicks. Some are tried and true and others are old time methods. It is difficult at the age that yours are at as they are in a great transition. When chicks are first hatched they can be vent sexed, feather sexed or color sexed depending on the breed. At six weeks, most chicks are fully feathered. On many breeds but not all, the pullets will get their tail feathers first. This is usually easiest to spot when they are about a week old. On newly hatched Barred Rocks you can usually tell by the spot on their heads. The pullets will have a well formed circle spot or no spot on their head while the cockerals spot will be larger and mis-shapened. On newly hatched chicks most can be feather sexed with the pullets having two distinct rows of feathers and the cockerals having what appears as one row. At the age of your birds now, you can check the hackle and saddle feathers. There should be new feathers coming in that will appear pointed on the cockerals and rounded on the pullets. But your best bet now is to wait another 6 weeks and it will be quite evident of which are which. Plus the cockerals should start trying to crow at 12 to 16 weeks. Depending on the breeding stock you got your chicks from you could expect your first eggs anywhere between 18 and 28 weeks of age.
