Consider this. Would you expect two thin cardboard boxes hot-glued together, curved into a vague semicircle, held there by string and a cardboard tube handle, painted in red and yellow, to make an effective shield against an actual honest-to-god hunting knife? On the previously-mentioned school LARP day, somebody came as a ranger from Ranger's Apprentice. After withstanding plastic lightsaber strikes and slashes from a plastic Zorro sword without even a scratch (which is to be expected honestly), I ended up facing the 'Ranger' in a duel. Because fighting with ACTUAL weapons was prohibited, we tested the effect of the knife on the shield by slashing and stabbing it. When stabbed at full force, the knife only just went through both layers of cardboard, and actually scraped off the shield boss (which was a devondale butter lid painted white). All that a slash did was scratch the paint and the first layer of cardboard.
This was a MODERN and SHARP hunting knife put up against a CARDBOARD SCUTUM. Since the LARP, I patched the front up with masking tape and painted over (and it actually looks like it has taken war damage and been patched up). Last weekend, I propped the shield up against a hay bale and shot it with my longbow. The arrow did get through quite a considerable way, but still not enough to hit the hay bale. My second arrow actually penetrated the first layer of cardboard, but skimmed off the second layer and got stuck inside the hollow section of the shield (the arrow actually made it fall off the hay bale this time).
What I'm trying to say, is that sometimes something that is shoddy may be 'good enough' against something that is exceptional. Would you expect two cardboard boxed glued together to be able to withstand a sharp steel knife? Would you expect it to be able to stop an arrow fired from a MODERN longbow? What's more, I can even post pics of it once the school puts them on FB
EDIT: When I was making the shield, the art teacher asked what I was making and I answered 'Scutum'. He stopped what he was doing, blinked and took a step backwards. Then I said 'It's latin for shield' and he answered, 'That's good, because I thought you said scrotum'
Then I said, "That's right, I'm making a cardboard scrotum" sarcastically and now I have a bad feeling that this is going to be OOCQ'd