Curriculum change
For specific notes on physics curriculum, please see How physics educators shape the content of their curriculum.
In Science Curriculum Reform in the United States, Rodger W. Bybee summarizes some differences between science curriculum reforms in the 1950s and 60s, and the 1990s. [1]
Change can be lead by equipment
Nanoscale science, spectroscopy, electronics, and bio-technology are examples of modern fields influencing preparatory curriculum with fancy equipment. Secondary schools are buying electrophoresis equipment, computer-based spectroscopes, semiconductors, and other lab equipment that is not suited to teaching content from before these fields' existence. High-achieving students are going to college from school districts with impressive research science budgets, partly focused on regional and national science and engineering student competitions.