Introduction This study describes and interprets the subjective theories that a group of students from a public and state secondary school in the Atacama Region, Chile, hold regarding high-cost prosocial behavior on students with special educational needs (SEN).Methods A qualitative methodology was employed, with an instrumental case study design. A total of 11 students, selected through theoretical sampling, participated in the study. Episodic interviews and a focus group were conducted, with the data being analyzed using thematic coding, grounded theory procedures, and specific analysis of subjective theories.Results Findings show that high-cost prosocial behavior is linked to values of justice and inclusion, entails social risks for the benefactor, and has positive effects on well-being, educational inclusion, the academic performance of students with special educational needs, and school climate.Discussion Family, school, and group factors are discussed in connection with the promotion of this type of prosociality, highlighting its formative potential with a view to pursuing a fairer, more inclusive educational environment.