The pyramids could provide an interesting discussion on the limitations of scientific investigation. The pyramids have an aura of mystery. Think of their size, their alleged curses and the many different explanations for them.
The theory relating the shafts to star constellations encourages discussion about why the stars have had such a powerful influence over people's lives and why their position changes over time.
Science has extended our techniques of archaeological analysis; radiocarbon dating, X-ray diffraction analysis, resistive surveying and thermoluminescence to name a few. Discover thermoluminescence in class using ground up fluorite (Blue John) and heat it on a tin lid, being careful to wear safety goggles. Light comes out which has effectively been trapped in the rock. The intensity of light is related to the age of the rock and arises because over long periods of time the naturally occurring background radiation causes excitation of electrons in the crystal structure and defects. When the rock is heated the electrons are released from their excited energy levels and give out light as they fall back to their ground state.