A European initiative CODING4GIRLS (C4G) promotes the acquisition of programming skills through a game development process with the aim of preparing young learners, especially girls, to enter computer science careers and raising awareness of the relationship between ICT and the real world. Using the C4G game development-based learning methodology, students develop serious games for which they need to learn specific programming concepts. This paper presents the results of a study with a mixed-gender group of both boys and girls (N = 773) carried out with the aim of examining the effectiveness of the C4G development-based learning approach in lower secondary education in Croatia. In-service and pre-service teachers organized learning activities for students based on the C4G learning scenarios, which include the development of games in the programming language Snap! with topics that are interesting for both boys and girls and which involve solving real-world problems. The results showed that students accepted the C4G methodology and were motivated to learn how to program by developing games for solving real-world problems. Teachers and experts consider this approach as a relevant and effective method for achieving learning objectives related to programming, applicable and suitable for lower secondary students (11–15 year olds).