I believe that it likely begins at middle school or high school instead because this is the age an individual can more easily comprehend what computer engineering is actually all about. What I suspect is that generally speaking both men and women start out on equal footing in terms of having access to a computer to learn on and the capability to learn the craft. I suspect they are also on equal footing in terms of both feeling the same intellectual stimulation, challenge, rush, and sense of self-empowerment that comes after they've built their first program.
Unfortunately from that point on more male than female students go on to more fully grok programming. I believe this is because the hidden costs associated with pursuing the craft are unequal between the two genders. For either gender it can represent a 'ding' on their popularity scorecard so to speak, but the ding is felt far more profoundly for women. One can certainly debate why this is and of course it's possible to trace this phenomena historically back into the days of ancient greek culture and before.
My feeling on the matter personally though is that the cultural norms of highschoolers have simply not had time to adapt to the idea that "geek is sheik" because the sentiment has only existed (outside of hacker culture) for the last decade (and perhaps it's still only a thing in California). In addition to that there has never been a "female astronaut moment" for computer science, so to speak in terms of it breaking into the consciousness of the average teen. This may be a chicken/egg type problem.
I think this is shifting now, but my opinion is that the biases which effected how highschoolers were feeling 15 or 20 years ago about computer science are still skewing the hiring statistics today because there are far fewer women job applicants who have been doing this kind of programming work for 15 or 20+ years...
How many were programming BBS systems in ANSI C back before AOL was a thing, or how many were following along with the early web as the standards (things like CSS) were being flushed out and it's possibilities were being explored (intro https://www.youtube.com/watch?v=C_B31nF3sU0&t=2m10s)
According to the statistics there are a lot more men who have been engaged in "Internet engineering" in one form or another for most of their life and this kind of multidisciplinary computer-science background can skew a hiring decision in their favor assuming both candidates are equally well versed with the most current technologies. Young programmers find ways to make up for the often times narrower scope of their experience (lack of a lisp beard) by being really good at the things that they specialize in, and by tracking more closely the cutting edge. I feel there are more women who are joining this cohort every day, but there are still not as many and it's a shame.