It opens tomorrow. Go see it! It's so good!
The secret is that the Hailsham kids are clones created by the government from the tissue of ne'er-do-wells in order to provide organ transplants ("donations") for nonclones with janky livers and such. After graduation, they're sent out into the world—free-range clone kidneys!—where they're welcome to eat sandwiches, play soccer, look at porn, and fall in love for a couple of years before they die of not-having-lungs.
Read and comment on the whole thing HERE.
And if you're interested for some reason, you can also read my review in the Telegraph—it's exactly the same, except slightly longer and they took out all the swears. Cheers!