During the summer vacation children who are economically disadvantaged experience declines in reading achievement, while middle- and high-income children improve. Previous research has demonstrated that the most widely implemented intervention -- sending economically disadvantaged students to summer school -- has not led to increases in reading achievement. In this longitudinal randomised trial, a randomly assigned group of exiting First-Grade children who were economically disadvantaged was enrolled in a seven-week summer reading day camp. The intervention students' reading achievement was then compared to control group participants at four time points. Results showed noteworthy differences for intervention students in reading comprehension.