Childhood sun protection is important to reduce the risk of developing skin cancer later in life. An evaluation of an expanded version of the Sunny Days, Healthy Ways sun safety instructional program was conducted with 744 students in 77 kindergarten to fifth grade classes in 10 elementary schools. Students in six schools received instruction twice over two school years. Students in four schools received it only once in a single school year or were enrolled in a no-treatment control group. A single presentation of the sun safety materials improved sun safety knowledge in students in grades 2-5 (p < 0.05). Repeated presentation over 2 years improved all outcomes, including increasing self-reported sun protection (p < 0.05) and decreasing skin darkening indicative of exposure to ultraviolet radiation (p < 0.05). The program did not improve children's knowledge or skin darkening in kindergarten and grade 1. These results highlight the need to provide sun protection education over several school years, not just one time, to produce changes in sun safety behavior.