The SAT is a reasoning test. Therefore, it does not test students on subject-specific content. Instead, it tests students on their ability to apply reasoning and logic to all subject matter to ensure comprehension.
Students must be able to take the tools for reading, writing, and math that they should have learned in high school, and apply them to situations slightly different from those which they are accustomed to seeing.
This is a key distinction. Put in other words, the SAT wants students not just to know material through memorization, but to understand the principles and methodology for analysis and assessment of that material.
Remember, the SAT is testing the student's ability to approach material, any material: Shakespeare, history, science, anything. Here's what matters: does the student have the tools in place to read, comprehend, assess, and react?
Do students COMPREHEND the intent of the writer?Can they ASSESS the content of the passage and recognize what is important? Finally, can they REACT to a writing prompt and construct a cohesive argument for or against that topic.
If a student is not equipped with the math, reading, and writing skills necessary to approach new material, then that student will encounter problems as he/she moves on to the more challenging college curriculum.
Most people think that undergraduate college prepares you for a specific career path in life. In reality though, college teaches us more about "the art of learning." That is, as undergraduates, we learn how to learn. We enroll in courses that will force us to take our level of knowledge in a subject area and apply it to the next level up. In college and life beyond, we are constantly asked to perform in places where we are uncomfortable and unfamiliar, yet able. At its ideal then, secondary education, as a precursor to college, should prepare students to be able to learn how to learn, and the SAT is testing the level to which students have been prepared.
Try not to get mixed up in the argument that some students are not test-takers and for others still, the SAT does not test their strengths. Remember one thing: at the very minimum to be ultimately successful in life, everyone graduating high school should be able to read, write, and do math at a level sufficient enough to survive in college. Reading, writing, and mathematics are at the foundation of everything in life. These are the subjects upon which the SAT focuses, and that is why it is a GREAT TEST.
The purpose of the SAT is not to look for a student's ability to memorize facts, or recycle an old research paper, or display knowledge of math concepts learned the year before. Instead, the SAT is looking to see if you have gained the reading skills to be able to read for critical information; if you have gained the writing skills to put together a cohesive, well-written essay that can engage a reader; and if you have learned high school math concepts well enough to apply them to questions that seek similar answers, but which are asked in unfamiliar formats. If you can do those three things successfully, you can move on to college and beyond.