Simplify the following text for a Grade 9 native English-speaking person.
Original: With Cecil King ( Rothermere 's nephew ) in charge of the paper 's finances and Guy Bartholomew as editor , the Mirror in the late 1930s transformed itself from a conservative , middle-class newspaper into a left-wing paper for the working class .
Simplified: In the late 1930s the paper moved from being a conservative , middle-class newspaper into a left-wing paper for the working class .