You mention that the math involves addition, subtraction, fractions - just ensure that they are teaching multiplication and division as well. Though, I think that if your DS is good at these topics, he should be doing more challenging math work (probably be moved on to preAlgebra). I believe that in most schools, the grammar topics change more often than once a month. There should be a "Creative writing" component to LA where they should be taught to write short paragraphs, short essays, book reports etc. Also, I don't see an emphasis on science, but, I think that it is normally included in the school day at this age as is a separate History or Geography curriculum.
I do like the logic puzzles/venn diagrams that your son does every day and the freedom to read etc. The extras sound great.
