According to the PISA and TIMSS results, Kosovo is among the low-achieving countries in mathematics. Analyzing the factors that contribute to this situation is a local priority. This study focuses on secondary school students' beliefs and attributions related to the level of impact of four main groups of factors (student characteristics; teacher characteristics; school and classroom environment characteristics; and home environment characteristics) on achievements in mathematics. Respondents in the study were 410 students, randomly chosen from eight secondary schools in Prishtina. A Likert scale questionnaire was used for data collection. The reliability of the questionnaire was checked using Cronbach's alpha. The descriptive analysis was used to measure the students' answers according to the four subscales (groups of factors). To explore the effect of gender and the type of school attended on students' opinions, independent samples t-test was used, while one-way ANOVA served to explore the effect of success and age. Students believe that teacher characteristics are the most critical determinant for achievements in mathematics. According to students' opinions, the order of the impact of the groups of factors, ranked from highest to lowest, is teacher characteristics; student characteristics; school and classroom environment characteristics; home environment characteristics. The findings revealed no statistically significant effect of gender on students' opinions. There were some differences in students' opinions based on the type of school, age, and success. However, the effect size of the difference was considerable only in the case of the type of school attended regarding the influence of teacher characteristics.