Augmented Reality (AR) is now being used in education across various subjects. The number of AR applications has increased with the popularity of smartphones. In this study, we explore the use of AR-based apps for teaching astronomy in the last four years of secondary education in Spain. The study includes an experimental group and a control group to show the benefits of using AR in the classroom. We conducted a pretest-posttest design, with a knowledge questionnaire given before and after the teaching period. 130 students aged 12 to 16, from a secondary school in Spain were divided into four groups, each having a control and an experimental group. The experimental group showed significant improvement in academic performance through the use of AR. This research aligns with previous studies, confirming that the use of AR makes Science, Technology, Engineering, and Mathematics (STEM) learning more engaging compared to traditional teaching methods.