Fourth-grade science: It's when you start to get a sense of not only how the world works, but also of why your parents used to get so nervous when, a few years before that, you would insist on asking things like, "Why is the sky blue?" and then if they could answer, follow up with, "But why does light act like that when it hits the atmosphere?" It's a matter of starting to see that first, the world is incredibly complex, second, that it takes a specialist to really understand it in detail, and most of all, it's your first glimpse of how the underlying principles that make all of existence work are actually universal, elegant and at least a little bit comprehensible to the human mind.
From the fractional distillation of crude oil to the photosynthesis taking place in all plants to the first encounter with a hypotenuse, Fibonacci, and sublimation, fourth-grade science opens up a whole lot of possibilities. Well taught, it can funnel a smart kid into the world of STEM studying and a fulfilling career, while inculcating those less scientifically minded children with a sense of wonder and curiosity. Poorly taught, of course, it can take a potential lifelong interest in science and strangle it stone dead. Let's see which of these your teacher did!