Earlier quoted context omitted.
For one indication, look at the ratio of women to men graduating from STEM courses in universities. Even in school, the number of women taking STEM subjects is dwarfed by the number of men. While the issues another poster has mentioned (uber etc) I'm sure do not help the situation, it's still a huge problem even at school ages.
No, this claim is false for any reasonable definition of "STEM" and "dwarfed".
At GCSE level (roughly aged 15/16) there's an equal split across STEM subjects. For A levels, there's more men than women in every STEM subject bar biology, and women achieve higher grades on average.
At university level, men dominate in most of the subjects (engineering is 86% male and CS is 83% male). The problem stems far deeper than the workplace, and is definitely present in Educatikn.
[0] https://www.wisecampaign.org.uk/uploads/wise/files/WISE_UK_S...