Your Polish have their cockerel saddle feathers in. The pointy, glossy feathers on the lower back that are noticeably different from the surrounding feathers are exclusively male.
For the reds, compare the combs now to the combs they have at 8 weeks. Big change = cockerel, little to none is very likely pullet. I can't see the wing bows in your photos but a dark patch there is also a cockerel sign.
The barred Rocks have female coloring. If they came from a reputable...
You don't want to compare them with Rangers as those are bred to reach a large size very quickly. That said, they do look pretty darned small. It also looks like two of them have white skin? I'm thinking maybe they're mixes?
Coloring of hybrids is generally more variable than "pure bred" so I think it's likely they are all Amberlinks. I'd guess their age to be more like 3-4 months but maybe they're delayed from a sub-par diet.
Unless they're adults, ignore the tail. Baby tails can look curled and ragged from roosting on the floor. It means nothing whatsoever.
Some cockerels are obvious by comb growth, others have gender-specific patterning. Giving more information and photos makes all the difference.
X2. Silver based birds, in particular, seem to flush easily and their pinkish shades pop more in photos. But, there is zero comb development at this time and no sign of male patches coming in.
There is a lot more to SOP than leg color but the SOP calls for slate legs (dark wash on white skin) and yours appears to have dark wash on yellow skin (yielding willow or green legs).
First photo features a buff Orpington pullet. Second has a RIR pullet with another that's facing away (I'd want to see that one in profile because the wing shading looks a bit suspicious).