Gents, let's get hold of ourselves, here. According to the "hoax", if that's what you choose to believe, 20 kids need to play dead. Let's say, conservatively, that each kid has both sets of grandparents, three sets of aunts/uncles with two kids apiece, and of course mom and dad. That's 18 extended family members who are first cousins or closer to each pretend victim. For the moment we'll discount all the adult victims and the friends, friends of friends, and so on. That's 360 people who are intimately acquainted with each child, 360 people who need to either be in on the hoax or lied to. That's an awful lot of people already. Now we'll suppose that each minor victim has 10 friends. Shit, now we're up to 3,600 people who need to either be convincingly lied to by people they know very well, or who are in on the hoax. That's an ass-ton of people who are in the secret of the second gunman on the grassy knoll, and we haven't even counted all the police officers, faculty members, morgue staff, hell, I don't know who else who would have first-hand knowledge of what happened.
Do we really believe that 3,000 people could be lied to/bought off/whatever without a single one of them saying, "They're saying my best friend Johnny got shooted at the school, but I seen him get in a black hellercopper and fly away!"