nope, that's assuredly a boy. No pullet would have a comb and wattles that big and pink this early. They shouldn't start coming in on a pullet until 15 weeks at the earliest.
Oh, if it's a boy it's not really a big deal. I'm just trying to decide which to keep at my school and the that one is the kiddos' favorite. They call it Chicory.
That gray one looks so much bigger than the other 2 in that picture... I think the gray one might be a pullet, so you can keep hoping... These are mixed breed birds and hard to compare with each other...