I actually experienced breaking a toilet lid by sitting on it once (I’m like 70 kg). It wasn’t even one of those crappy ones. The problem was that it was designed with a slight upward arch and far too few points of contact with the seat, so if you sat down in just the right way (and happened to have your wallet in your back pocket) all the force was concentrated in the perfect way to make it crack.
I used to sit down on toilet lids without batting an eye, but now I am scarred.
Another comment here gives an example of how a 6th grade reading comprehension test could be formulated. Essentially, it’s about how complex sentences you can parse, and how large your “context window” is while reading.
Imagine a small child just learning to read. They struggle with every word, so if a sentence grows more complex than “The dog is brown.”, they simply can’t get to the end of the sentence while still remembering what the start was about. This also applies at a higher level: Keeping track of a complex “scene” which describes a setting while also describing dialogue between characters and inner dialogue in parallel requires more cognitive effort than the simpler “scenes” in children’s books. A higher reading level means you spend less cognitive effort actually reading and understanding the words and sentences, so you have more cognitive capacity in reserve to actually understand the full picture.
The US literally beat the Nazis to developing fission technology, i.e. nukes (admittedly with a very international research community). It’s quite clear just from that, that the US had plenty of strong scientists before they brought in Nazis/Nazi collaborators from overseas.
As a complete side note: I believe it’s been speculated (by people who know much more about this than me) that Nazi research on nukes, among other things, was hampered by researchers like Heisenberg deliberately dragging their feet because they were forced to work on the projects but didn’t believe in the cause. I’m not meaning to clear the name of any Nazi collaborators, but pointing out that not all scientists working under the Nazi regime were necessarily nazis.