What is good advice for someone who's interested in robotics and needs to pick their high school subjects?

At the most basic level there are some core subjects which you need to get started in robotics:

• Mathematics - This is a must. You don't have to be John Nash, but a good grasp of algebra and geometry are essential to all of the subjects which make up robotics.
• Physics (or another science) - Having a solid understanding of science is important for all branches of engineering. Physics is particularly useful because it gives grounding knowledge in energy, electrical circuits, mechanics, material science and other key topics for robotics. However, all sciences are useful as they teach how to apply mathematics to real world problems.

Other Useful Subjects

Every country has a different set of subjects that are taught in schools, so it's difficult to specify a list which is applicable to everyone. So, instead here are the core skillset which is useful for robotics and some subjects which provide them:

• Computing and Programming - Programming is pretty important for robotics, so subjects like Computer Science and Information Systems are a great choice.
• Design and Technology - Subjects that can boost the practical side of engineering include Product Design, Graphic Communication, Technological Studies and Manufacturing.
• Specific Engineering Disciplines - Some schools provide subjects in specific engineering disciplines such as Automotive, Bioengineering, Electronics, Mechatronics and Mechanical engineering. All of these can be beneficial for aspiring roboticists.

Reference:
[URL:http://blog.robotiq.com/what-to-study-for-a-career-in-robotics]