Ahh, A 4-H question! I'm good at those!
Okay, at my country fair, we don't really do egg grading. We do some pullet and hen shows, with the pullet shows for birds under 1 year who have not laid yet, and the hen show for birds who are laying and over 1 year. You can sign up for what ever show you want to- breed shows, showmanship (my fav...) fancy/utility breed pairs and trios..... ect.
I don't know about your fair, but if they do egg grading for you birds, usually the judge ask for 1 dozen recently laid eggs from the hen you are showing. The simplest thing to do is to not give the judge any double yolkers, and instead use them for yourself!
On another topic- what breed are your pullets? If they continually give you double yolkers, keep a close watch on them- they might be prone to laying problems like egg binding or prolapse. If they are young pullets, they will usually grow out of it as they and their egg-layer systems mature.
If in doubt, make friends with other 4-H'ers in your club or county, and pester them for questions- there's a high chance that I'm completely wrong!