Immigrant students' school success is often hampered by limited second language (L2) proficiency, yet the effectiveness of different approaches to L2 support is unclear. Using a summer camp setting, we tested effects of (1) implicit support focusing on meaning of language by engaging students in language-intensive activities without drawing their attention to rules (operationalization: theatre program) and (2) combined implicit and explicit support focusing students' attention on both meaning and form of language (operationalization: theatre program and instruction in German as L2). A baseline group received no support. N = 149 third-graders with German as L2 participated. There was no effect for the implicit condition on L2, yet children in the combined condition performed significantly better in grammar and reading after the treatment than the baseline group. The difference for vocabulary did not reach significance. Three months later, a significant effect for the combined condition was only found for reading. (Contains 5 tables and 1 figure.)