In the context of the quote from the headmistress (apparently not a feminist), the thread is about glass ceilings and girls being limited by biology.
There is a wider point to be made about pay for domestic work. However domestic work is as much a man's as a woman's responsibility, and people who break through the glass ceiling and have higher salaries are more able to pay somebody else a good salary.
Equally, assuming there is no choice not to work, the childcare years don't go on for ever. More money means more options to support teenagers and pay for extra curricular activities rather than leaving them at home to get on with things after school and during the holidays.
There are always choices to be made, but I'm not convinced that limiting aspirations makes things easier or that childcare is a woman's problem. These are the things that the headmistress seems to be concerned with.