The objective of this research was to diagnose the influence of School Theater on the level of learning of oral expression of the English language in fifth-year students of the secondary level of a public educational institution in the region of Tacna, 2023. The current investigation corresponds to an applied type of research using a pre-experimental design. An oral entry exam was carried out with the reading of a theatrical script, through an evaluation rubric considering the three performance levels of the competence Communicates orally in English, according to the National Curriculum. The results showed a significant improvement in students’ oral expression. Before the intervention, 53.57% of students were at the initial level, 39.29% in progress, and only 7.14% had reached the expected level. After the implementation of the School Theater strategy, 60.71% reached the expected level, 14.29% reached an outstanding level, and only 3.57% remained at the initial level. The t-test for related samples yielded a significant difference (t = −10.990, p < 0.001), confirming the positive impact of the intervention. In conclusion, the application of School Theater significantly improved the oral expression in English of the students, demonstrating its effectiveness as a pedagogical strategy to enhance communicative competence in a foreign language.