Classical education was first developed in the Middle Ages with the trivium and quadrivium as being its essential parts. Classical education has moved through the centuries with each culture and age adding its own individual twist to its pedagogy.
Classical education is a good fit for most college prep homeschoolers. This method of education seeks to systematically teach its students all knowledge through a methodical framework. The Classical education movement seen in the U.S. over the past decade has been an adjustment of this same method. This education is founded upon the quadrivium or the teaching of mathematics, philosophy, astronomy, and theology. Today's classical education in its purest sense is still very similar. Within philosophy there is rooms for history as well as logic (critical thinking as coined today).
A classical education for your middle school student would include these topics and probably many more.