I have a study permit for Poland, but somehow I want to move to another Schengen nation (say the Netherlands). Is this possible using the same Study permit, or do I have to apply for a separate Study permit for the Netherlands?
Assuming you are a non-EU/EEA/Swiss citizen and your citizenship country has no separate agreement with the country you would like to move to:
Studies over 90 days in duration is not governed by Schengen but by national law.
Your student residence permit is only valid as permission to reside in the country that issued it. It gives you no right to free movement to other Schengen countries.
Your residence permit allows you to visit other Schengen countries a total of 90 days out of any 180-day period. If you want to study (but not work) in another Schengen country while respecting the 90/180 limit, you usually do not need a separate visa or permit.
If you want to study for a longer time, you would need to apply for permission separately from the destination country (the Netherlands, for example).