This is the 10849th most frequent Turkish word.
dersleri
"Lessons" or "classes" (plural form).
Here, 'dersleri' is used to indicate a specific set of lessons (math and science) that the students are engaged in studying.
Öğrenciler, matematik ve fen bilgisi derslerini çalışıyor.
The students are studying their math and science lessons.
In this case, 'dersleri' refers to an entire category of lessons (language lessons) that are being preferred or found interesting.
Ben genellikle dil derslerini daha ilgi çekici bulurum.
I generally find language lessons more interesting.
Here, 'dersleri' refers to specific sessions or classes related to art that are planned for discussion.