Tracking and ability grouping remain among the most hotly debated topics in Czech Republic education today. The Czech education system as in many European, particularly post-socialist countries, enables divide students into different tracks at elementary schools and high schools. For example Elementary schools "track" students when they divide them into separate classes for specific subjects or for the entire day. High schools “track” students when they divide students into academic, general, and vocational programs to their abilities (Gamoran, 1992). Tracking and ability grouping are common features of Czech schools. Tracking is separating students by academic ability into different groups, classes or schools for all subjects. Tracking differs from ability grouping by scale and performance - ability grouping is short-term. Ability grouping separate groups of students for particular subjects. Students are typically divided according to their abilities and school performance. According to the studies students placed in lower tracks ultimately achieving less than students of similar aptitude who are placed in academic programs or untracked classes (Loveless 1998). Low-track classes tend to be composed of low-income students, usually minorities, while high-track classes are attended by students from socioeconomically successful groups (Oakes, 2003). First, high-track students take more academic courses than students in low-track (PISA 2012). Second, high-track teachers are more enthusiastic and spend more time preparing. Teachers in low-track classes spend more time on behavior management and less on instruction (Oakes, 1991). This is the reason, why low-track students achieved less than high-track students. The aim of this research was to find out how do principals assign teachers to differentiated classes.

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