From my experience children and teenagers know very little about where their food comes from. My cousin entering grade 10 tried to tell me today that cows often die naturally and then we eat them. When I assured him I have watched how cows die and it is human caused he tried to argue with me. He couldn't accept that if an animal dies of illness, old age, or suicide that we cannot eat it because we'll get sick. My cousin isn't stupid, he's extremely intelligent; he's just part of a generation of children and teenagers that are not told where their food comes from. When they aren't told, they make it up from what they know. What they know is nostalgic images of open farming fields, how lions kill zebras, and how humans die of old age.When we don't correct them we encourage these lies they've accidentally made up. When they grow up they are so skilled at creating these alternative stories that the real story seems so far fetched and so impossible that they don't even stop to think about it. It simply isn't possible that cows often go through the process of being skinned and cut up alive. But they do, so where are we now?
I will never have children, but I know I don't have that in common with most people. Many humans look forward to starting a family and having children. Perhaps the last thing they think about is what they will tell their children about the food on the table, other than to eat it. If someone had told me when I was six that to get steak you had to kill a cow I'd never have eaten steak again. It's actually a logical reaction. To make steak someone dies. I don't want someone to die, so I won't eat steak. To eat steak even though I don't want someone to die would actually be silly.
Children and even teenagers are not always given respect, they are treated as lesser beings rather than equals. If we respected them more we'd tell them the truth about where their food comes from. We'd allow them to have all of the information so that they could make informed decisions on their own. Instead by not telling them we are deciding for them. We are removing their autonomy.
If you balk at the idea of telling children where their food comes from because it might be too horrible - why are you even giving it to them? Surely they'd disapprove. Therein lies your answer.