Every foreign student needs to have a Residence Card to stay in Poland.
Students from the EU needs Residence Card to legalise their stay after the first three formality-free months.
Non-EU students should apply for a Residence Card before their visa expires in one year.
A Residence Card is an ID card that proves that you have a residence permit. Together with your travel document it allows you to cross the Polish border as many times as you wish. It is issued for the period of your studies. You are allowed to travel through all the Schengen member countries as well as work in Poland if you have a Residence card.
REMEMBER: You should apply for the Residence Card when you are legally staying in Poland, which means after you arrive, but before the end of the three month period (EU students) or the expiration of your visa (non-EU students)