Given that Polish is the L1 here, outside of class, many Poles don't have much opportunity to practise it on the streets.
Many private school students are there because:
a) they have it offered at school but they don't like the classes
b) they're having trouble with passing tests at school
c) they think it will improve their job prospects
d) they think it will save their job if there are cutbacks
e) they think it's something they should do
f) it's a hobby like stamp collecting or ballroom dancing
g) someone else is paying (company, family member)
h) it's unfinished business (this time I'll learn something!)
Probably a small minority have real intentions about moving to an English speaking country or will ever have real need to use the language in any important way.
They're also not generally interested in questions of accents or various non-standard usage, they're there to learn their idea of English (which in their minds is an inferior kind of Polish with different words, insufficient grammar, bad spelling and confusing pronunciation).