This is the 464th most frequent Polish word.
klasy
"Klasy" in English means "classes."
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.
Styl tego samochodu to prawdziwa klasa.
The style of this car is truly a class act.
'Klasy' is used here to specify individual class divisions within a school schedule or system.