Upvote:14
Both Poland and France are Schengen countries, so you are not leaving the Schengen Area by flying between them. In fact, there will be no border control - the flight is like a domestic flight.
When your friends went to the UK, they were refused entry because the UK is not a Schengen country, but an "independent country" with its own border and a separate visa policy. Thus, a Schengen visa is not valid for the UK.
If you went from Poland via a UK airport to France, you would exit the Schengen Area when leaving Poland, and would not be able to re-enter it in France.
However, if flying directly from Poland to France, you are not leaving Schengen, so you will have no problems