The biggest hurdle for most people seems to be how to get a formal mentor and how to become one. I spoke on this subject at a conference for women entrepreneurs and at the end of the session I had exactly one woman approach me.
The best mentoring relationships happen organically, where you click and connect with someone else. There has to be some chemistry. You need to like and respect each other. You need to enjoy spending time together. When you are "matched" by someone else that element is not always there.
Science, Technology, Engineering, and Mathematics (STEM) is an important factor to our society. Girls' accomplishments in STEM are created by the quality of female leaders around them. Once young girls see themselves as successful as the leaders before them they will believe in the potential for academic growth therefore a positive outcome will result out of it.