This is the 4122nd most frequent Polish word.
białostocką
"Białostocką" is the feminine accusative or instrumental form of an adjective meaning "related to Białystok," a city in Poland.
Here, 'białostocką' is in the instrumental case as an attribute of 'ulicą', describing the street associated with Białystok.
Spaceruję białostocką ulicą.
I am walking along the street of Białystok.
Here, 'białostocką' is in the accusative case as an attribute of 'szkołę', indicating a specific school that is related to Białystok.
Zobaczyłem tę białostocką szkołę.
I saw this school from Białystok.
Here, 'białostocką' is in the accusative case as an attribute of 'tradycję', referring to a type of tradition from Białystok.