You can’t change your class. I’m not talking about your descendants but you as a person, in your life.
Class isn’t so much about money or what job you have. It’s about upbringing, connections, thoughts, and opportunities.
Colleen Rooney is very wealthy but she will always be working class.
Kate, Princess of Wales, could lose her status and live on a council estate on benefits, but she will always be middle class.
Class is not dependent on money or job title, it is deeply ingrained and can’t be changed in you.
If you are working class and do well in life then there is a possibility that the descendants you have will start to lead a middle class lifestyle in time, but like I said, class is very much about upbringing, connections, thoughts, and opportunities and those sort of things ‘stay’ in their classes.
ETA: this is why class is most unfair on the working class because it does create a barrier in many parts of life. Whether people like it or not class is absolutely alive and kicking in the country.