All the tests from the Mandelbrot Competition for the years 1990 to 1995. The Mandelbrot Competition is one of the most challenging and educational high school contests in the United States. Answer keys and hints are provided for the Individual Test questions, while full solutions explain each Team Test.
Individual Test questions are excellent training for the AMC and AIME contests, and the Team Test questions are excellent training for students first learning how to tackle challenging proof problems. This author is a past US International Math Olympiad team member.