I'm guessing your feed store orders from Ideal...and based on age and backing up three weeks for laying, it was probably still pretty hot, so don't be surprised to get a lot of boys (this per one of the local chicken breeders/hatchers that supplies a few local stores)
1 - if buff sebright, it's a boy because it has a noticeable comb already
2 - blk frizzle cochin definitely boy, I got two of those! And they're fiesty!
3- oegb? unsure, showing comb, how old? Boy?
4 - Red frizzle cochin see #2
5 - Buff brahma - I was going to say boy, but then read it's younger. They are a breed where boys tend to feather out more slowly, so watch for that. It could be a mille fleur d'uccle? Are those muffs or just the lighting? See #13
6 - white cochin, unsure, what age? guessing boy
7- white frizzle cochin, probably boy
8- white cochin probably girl
9, 12, 15, 16 - silver and golden sebrights - if they show any sort of comb early on, they are boys! You will see the difference easily between the boys and girls.
10 - ?? looks girl
11 -Buff cochin, probably girl
13 - Blue mille fleur d'uccle? Are those muffs in the picture? Legs don't looked feathered enough for partridge cochin. Too young to tell, but if it's a d'uccle, the comb will develop rather early if it's a boy.
14 - black oegb, I'm guessing boy but not sure
Out of 18, I ended up with only 8 girls.