COS:

Frank Szmulowicz, Ph. D. Sep 3, 2022:

This refers to Warsaw (Warszawa), Poland (PL). Czesne is Polish for tuition.
COS could stand for an academic institution. For example, Centralny Ośrodek Sportu (COS) is Central Sports Center that trains olympians. However, they are funded by the government and do not charge tuition to Polish athletes.


Centralny Ośrodek Sportu
The Central Sports Center is an entity specialized in sports training of Olympic and national teams, both seniors and juniors. It has six Olympic Preparation Centers: in Spała, Władysławowo, Giżycko, Wałcz, Szczyrk and Zakopane.

The basic COS is to provide conditions for sports training conducted by Polish sports associations and other entities dealing with physical culture, including, above all, creating conditions for the training of the national team to participate in the Olympic and Paralympic Games, deaf Games, European Championships and World Championships.

COS is a budget production subordinate to the Ministry of Sport and Tourism. Local office in Warsaw, in the COS Torwar hall at ul. Łazienkowska 6a.
https://cos.pl/en/1/centralny-osrodek-sportu