Pullets, of the barred rock variety will appear to be darker barred than the cockerels will. They will also not develop such a large comb, so early on. Sorry to say, the lighter appearance to the barring, and the comb size already, indicate that this is a cockerel. His comb will get larger and more red over the next few weeks.
I would defiantly say that is a cock. With Barred rocks and Plymouth rocks if the barring is lighter they are cockerels, darker barring and they are pullets.