The aim of this study was to better understand the gaps between policy and practice in inclusive education for the Republic of Serbia. The study compared the academic achievement in Mathematics of comparable students with mild intellectual disabilities (MID) in the fifth and sixth grade who attend typical elementary schools and special schools. A total of 249 students participated in the study. All students were either 11 or 12 years old at the time of the study and were matched by ability, based on local educational and psychological assessments. Results indicated that students with mild intellectual disabilities who attend special schools scored significantly higher on mathematics achievements in comparison to their peers with similar disabilities in regular schools. Although the aim of the Republic of Serbia's new education policy focuses on inclusion, preliminary research indicates that students may be integrated (not included) and that regular classroom practice may not be supporting students with disabilities. A closer look at strategies that appear successful in special schools (such as adapted teaching strategies, work in small groups of students, and continuous individualised support of teachers) may provide instructional insights for newly included students in Serbia.