This article reports on a year-long study of high school students learning computer programming. The study examined three issues: I) what is the impact of programming on particular mathematical and reasoning abilities?; 2) what cognitive skills or abilities best predict programming ability?; and 3) what do students actually understand about programming after two years of high school study? The results showed that even after two years of study, many students had only a rudimentary understanding of programming. Consequently, it was not surprising to also find that programming experience (as opposed to expertise) does not appear to transfer to other domains which share analogous forrnal properties. The article concludes that we need to more closely study the pedagogy of programming and liow expertise can be better attained before we prematurely go looking for significant and wide reaching transfer effects from programming.