How can you tell a hen from a rooster at 11 weeks old....I have 3 Barred Rock and 3 Buff Orpington? We were told at birth they were all females....have our doubts! What do we look for? There is no picture....sorry!
Barred Rocks are easier to sex at hatch, just as soon as they are fluffed out, by three traits taken together as a group: leg color, head spot size and edge definition and down color. Most BR males, even if you haven't sexed them when they hatch get red combs by less than six weeks of age. A Buff Orpington is not as easy. You have to wait for that big red comb, then you see the pointy shiny saddle feathers that only roosters have come out after about 12 weeks of age.
Did you get them from a hatchery? Those usually vent sex the chicks when they hatch, an art that us mere mortals rarely learn, though it would be handy to be able to do with breeds that don't sex easily until much later in life.