> for some reason Edit: I was sort of right, but I found this on the website: “We chose fourth graders because research shows that kids ages 9 to 11 are begin

> for some reason Edit: I was sort of right, but I found this on the website: “We chose fourth graders because research shows that kids ages 9 to 11 are beginning to learn about the world around them. They're open to new ideas, and they are likely to connect to nature and our history,” Original answer: 5th grade is the year that students learn about US History. I think the theory is that they get a chance to see the national parks before they learn about them in 5th grade.