Entry requirements for EU citizens:

The citizens of EU member state to enter Poland need only a valid travel document or a document confirming identity and citizenship (i.e. your national ID).

For a stay shorter than three months there are no formal requirements. However, your studies will take longer. For such a stay a registration of residence is necessary. You should register with Voivodship Office.

Link to the website:

https://migrant.poznan.uw.gov.pl/en/procedury/registration-stay

Address:

Wielkopolska Voivodship Office
Plac Wolności 17, 61-739 Poznan, 4th floor
cudzoziemcy@poznan.uw.gov.pl