There are three main possible ways to do this.
First, the country can try to ensure that there are plenty of good (and well-paid) jobs for people who major in these areas. It stands to reason that students will gravitate towards fields in which it is possible to make a good living.
Second, the country can try to make it easier to afford to study these subjects. It can provide more scholarships to people who go into these fields.
Finally, the country can do more to promote good teaching in these areas. Perhaps it could push for higher pay for science and math teachers who are shown to do a good job of educating their students. Paying really good salaries to good high school math and science teachers might attract better teachers who can inspire students and help them to succeed in this rather difficult subject area.
Research indicates that you should start the process no later than middle school, especially for girls. You need to create problems based on concepts that the youth can understand. I suggest we introduce and promote mobile app programming and cyber security. These are topics they can relate to. cyber security is a different look at basic networking and computer security combined. There are regional national competitions starting at the high school level. A community college in California beat Dartmouth at the national level. The benefit of building mobile apps should be obvious to our youth and us older folks. The iphone apps are created in a form of C. The androids use java with the eclipse platform. You can start introducing these concepts within the existing Cisco, other networking programs, and mainstream programming classes. Introduce modules of the cyber security or its possible competions in the networking classes. Introduce modules of programming simple mobile applications in a basic programming class. Yes you need Macs to do the iphone programming though multi platform software is available. Yes you need alot of math. We may need to teach more classes or teach each class better. But the idea is to promote these subjects mentioned early like in the middle schools and high schools. Community colleges should create consortiums with the local high schools. That is where the grants seem to be going. There is more emphasis taking CTE classes to enter colleges. Emphasis networking is important. Programming is important to all engineers and scientists. Push mobile app programming and cyber warfare. We expect shortages in both fields. We can make a good living and also have fun.