Contribution Results of international comparative studies like Programme for International Student Assessment (PISA) have shown that a large group of fifteen-year-old students do not even reach the minimum standards of mathematical and reading literacy (OECD, 2010). Especially in Germany more than 15 per cent of the students in the lower secondary school (“Hauptschule”) belong to this low-achieving group. But how could their competencies be increased? One possible way is the implementation of summer programs. On the one hand to strengthen their academic achievement and on the other hand to prepare them for vocational training. In a meta-analysis with 94 studies from the US, Cooper et al. (2000) found out that summer programs show an average effect of one-fifth standard deviation. Especially remedial programs seem to have a positive effect on students learning. For Germany there are only few results released concerning the effects of summer learning programs. Stanat et al. (in Press) compared the effects of implicit and explicit support for second language learners in the primary school. They had found out that the combination of implicit and explicit learning shows better results than an implicit learning treatment only. The present study focuses on the effects of a three-week summer program in Germany. Our research question is: Which effects does the summer program have (a) on mathematics achievement, (b) on reading achievement and (c) on academic self-concept of the participants? Method The summer learning program that is evaluated in this study was developed and organized by the University of Lueneburg in Germany (Czerwenka 2008). Altogether, N = 113 low achieving students from 8th and 9th school grade participated within three summer camps in different locations of Germany. The students were, on average, 15;4 years old (SD = 0;9). There were 53 per cent girls and 47 per cent boys. The duration of the summer program was three weeks and the students were trained in mathematics, reading strategies, and in vocational behaviour patterns. Besides that, secondary skills are trained in projects like theatre and marketing. The overall aim of the summer learning program is to strengthen students’ academic achievement and to raise their academic self-concept. The effects of the summer learning program was analysed by a pre-post-test design. The test for mathematics achievement consists of 46 items from six mathematical content areas (Cronbachs α = .86/.87). The reading achievement was measured by 70 items of a standardized reading test (Cronbachs α = .89/.89). The academic self-concept was evaluated by a 10 items scale (Cronbachs α = .85/.86). For the analysis, the data was scaled by using IRT methods. Expected Outcomes The overall results of the summer learning program show positive learning gains on all three scales, but the size of the effects differ between the three test instruments. In reading achievement the increase is on average about half of a standard deviation (d = 0.51, p < .05). Girls as well as boys could gain from the reading support in the summer program (girls: d = 0.56, p < .05, boys: d = 0.48, p < .05). For the academic self-concept the overall gain is about d = 0.38 (p < .05). Here, the increase for girls is higher than for boys (girls: d = 0.41, p < .05, boys: d = 0.38, n. s.). For the mathematics achievement no significant increase could be observed (d = 0.27, n. s.). Comparing the learning gains between the three camp locations we find different profiles of learning success, even though all three camps followed the same teaching curriculum for the summer learning program. The results will be discussed with respect to student’s differences in pre knowledge and academic self-concept between the camps. Finally, implications for the conceptual design of summer learning programs will be drawn.