Normally when sexing chickens you can determine a rooster by its comb. Roosters combs turn red faster than a hens, so normally by the time the chicks are 6 weeks old you can determine which ones are roosters because their combs are red and the hens aren’t. I wait till my EE’s and Americaunas are...
My guess is it’s a Whiting mix. Whitings are harder to sex because the pullets tails tend to look more like a roosters. They are normally longer and have more of a sheen to them compared to most other breeds.
I’m still going with pullet…..but how old is he/she?