The State Matura is an important part of the Croatian education system, both as a graduation examination for the completion of upper secondary, grammar school education and a matriculation examination for admission to higher education. When it comes to students with disabilities, their success at the state graduation examination can be an indicator of the inclusiveness of the education system because the possibility for students with disabilities to take state graduation exams and their appropriate achievements suggest that inclusive principles during primary and secondary education have been respected. The first State Matura exams in the Republic of Croatia were administered in the school year 2009/2010, with the same model of examination technology adaptation applied since then. Students with disabilities were given the same State Matura compulsory and optional exam contents and levels (higher and basic) as the non-disabled students, but with adjustments to the exam materials and/or procedure. The aim of this doctoral dissertation is to examine the achievements of students with disabilities who sat the technologically adapted State Matura exams in Croatian, mathematics and English at higher and basic levels in the school year 2009/2010 and 2010/2011 and thus test the functionality of the current exam technology adaptation model. All data related to students, results and grades were collected with the permission of the National Centre for External Evaluation of Education from the following databases: NISpVU - National Computer System for Applications to Higher Education Institutions, SRDM - Central State Matriculation Register and the internal database of the National Centre for External Evaluation of Education. For the data processing, univariate methods were used for calculating basic statistical parameters and testing the normality of frequency distributions (arithmetic means, standard deviations, the Kolmogorov-Smirnov test and the Shapiro-Wilk test), the T-test for independent samples, ANOVA and Rank Sum Test (the Wilcoxon test and Mann-Whitney's U test), Pearson's chi-square test and Spearman’s test. The analysis of the results provides an insight into the individual characteristics of the population of students with disabilities who took the State Matura exams with the adaptation of the examination technology and their level of educational achievements. Differences in student achievements and a correlation of student achievements at the State Matura exams and their average grades in the corresponding high school subjects have been established. One of the indicators of the functionality of the model is the (non-)existence of differences in the achievements of students with disabilities who took the exams with the adaptation of the test technology and of students without exam adaptations in certain tasks concerning Croatian, mathematics and English at higher and basic levels in the school year 2010/2011. Regarding renewed professional discussions about the educational achievements of students in homogeneous and heterogeneous classes, the (non)existence of differences in the achievements of students in inclusive and non-inclusive classes was examined. Additionally, data on the perception and the results of the support of personal assistants to students with disabilities from the school years 2011/2012 till 2020/2021 were analysed and the predictability of certain factors that influence the achievements of students with developmental disabilities was established. The key limitation of this research is the fact that none of the used databases contain data on the socioeconomic status of the families or the examinees themselves, qualitative indicators of teaching and learning methods, the school's inclusion index and many other factors that can affect the educational achievements of students with disabilities and/or the entire population. Therefore, the research was conducted on the basis of available databases and does not allow us to draw conclusions about the causes and consequences of proven differences in the students’ achievements in the State Matura exams. Nevertheless, this research offers insights into the established examination technology adaptation model and allows for improvements to the existing model by creating new adaptation forms in order to further reduce the differences in achievements among students and to raise educational inclusion to a higher quality level, including, of course, inclusion at the level of higher education, which ensures education equity. The contribution of this research is multidimensional. On the one hand, this paper provides information about the external evaluation process, the introduction of the state graduation examination into the Croatian education system and the development of an examination technology adaptation model in state graduation examination that enables equal students' opportunities. On the other hand, considering that in the Republic of Croatia no research has been conducted on the achievements of students with disabilities and the existing examination technology adaptation model in State Matura exams, this paper has an original scientific contribution. It provides an insight into some population characteristics, into the achievements of students with disabilities in the State Matura exams and gives guidelines for future research and practice with the aim of improving the quality of external evaluation of the achievements of students with disabilities, which contributes to ensuring and strengthening education equity. In the end, this paper may have historical significance in the future because it describes the State Matura examination and the adaptation of examination technology for students with difficulties and/or disabilities in the first years of one of the most significant changes in the Croatian education system.