No, the curriculum is not too difficult or elementary school kids, because the students learn the material. The biggest challenge in elementary school is that there is a wide range of abilities in a single classroom. It is hard for one teacher to address many students that are on as many different levels, but students are learning.
Elementary children are at the peak of their ability to learn. If anything, it should be harder and teach more since they are able to obtain that information. We are a nation of idiots. Children should learn as much as possible even at a very young age so they can grow up with a head start in life.