Not AT hatch, but within the first week you can do it pretty accurately by looking at the shape the wings are coming in and the tail. The pullets will have a sideways tear drop shape to the wing within a few days and the males are more blocky shaped, along with pullets have something of a tail coming in. There are a few breeds I know I can sex this way in about 5 days from hatch. Other breeds all grow in the same.Wait, you can sex Buckeyes at hatch? (Please forgive me, am new to the breed. And haven't gone back to read through this thread, either.)
Shellz middle picture of the one chick is a pullet. Compare it to the one in the bottom picture right in the middle by the water pan, which is a cockerel. Some people don't believe me, but I have had others try doing it this way and they come out almost 100%. It is nice knowing this, but for me, I keep just about all the ones I hatch so I have a good selection for the next breeding season. For folks who can't keep males, it is a useful thing to know early on.