Could depend on what areas of math and CS. Algebra and number theory are relevant to cryptography, for example.
I don’t disagree with UCB. It is just that so few people in CS work in cryptography and it is hard to find a job in that field
^ They do, they just can’t tell you about it. 
D’s school requires a CS credit, so she took it this year (freshman) to get it over with … and decided it wasn’t all that bad. I don’t think she will major in it, but she is glad that she is being exposed to it and feels it will help in the future.
I have two kids with strong computer interests. D16 completed Code Academy courses in about 6 different languages She is now a first year CS major and loving it so far.
S19 started as a 7th grader by pouring though DH’s college textbooks and various O’Reilly manuals. He has taught himself a huge variety of programming languages and spent this summer work on writing his own language. He shows no interest in programming anything practical but loves paying with coding for the shear joy of it. He doesn’t want to do AP comp sci because he hates JAVA. I understand very little of what he is talking about.
How young?
If on the younger side, I strongly recommend a gift of Lego Mindstorms.
It’s been years since I coached an FLL robotics team, and the product has evolved, but the visual programming environment was an EXCELLENT way to teach basic programming concepts (input, output, loops, if/then, etc).
In addition, instead of “Hello, World!” they get to see real, physical results of their programming also.
Most importantly, it’s really frickin’ fun!
Several members of my robotics team (2009 County Champs!) have gone on to STEM majors, including a new freshman at a single-digit-acceptance CS program. (He would have done it without me)