This is the 464th most frequent Polish word.
klasy
"Klasy" in English means "classes."
'Klasy' is used here to specify individual class divisions within a school schedule or system.
Każde dziecko uczęszcza do swojej klasy.
Every child attends their respective class.
Here, 'klasy' is used to refer to groups of students within an educational institution, a common usage.
To są klasy w naszej szkole.
These are the classes in our school.
In this sentence, 'klasa' (singular) is used metaphorically to signify high quality or elegance.