Mermaid, my DS in 7th grade is taking the SAT in January, too! He's in our advanced program, and this is something thru Johns Hopkins University, where they have "enrichment" activities/classes for kids. When he was in 3rd grade, he took the 8th grade standardized tests to qualify for Carnegie-Mellon University's enrichment program.
damo, the theory behind having kids take these tests so young is because it's felt that they're so advanced that the regular standardized tests for their grade level don't really measure their ability - they "top out" on them. So these kids take tests way above their grade level to see exactly how advanced they really are.
I kind of look at him taking the SAT in 7th grade as a fantastic opportunity - there's absolutely no pressure on him to get a good score. And he'll see what the SAT is like so when he takes it "for real" in high school, he'll know what to expect.
As for homework, both my boys are doing stem and leaf plots and I have no idea what they are. Simple subject and simple predicate? English/spelling - write the definition of the word and then give a synonym and antonym. Ok, but what's a synonym for saliva? Or an antonym for trellis? Ugh!