If that is the case then I would say giving a high level over view of pretty much everything about computers is probably what you want. Individual areas can become very deep and diving too much into the specifics will be time consuming and will not likely to benefit kids who do not go into that area.

Some topics off the top of my head that are pretty good for providing a broad understanding that could likely be used by everyone are:

-Typing

-basic browsing of computers

-Hardware vs Firmware vs Software

-How the internet works

-Browsers

-Concepts of basic security and protecting your information online

-Main parts of a computer and what are they responsible for

-Troubleshooting basic computer problems

-What programming is

-How to use commonly used programs (ie word, excel, powerpoint etc)

I think areas like these are good to give someone an idea of how computers work, how to use them on a day to day basis, and how things relate to each other. But I don't think that this is really enough material to cover four years worth of learning.

Some areas that maybe useful to teach kids about but won't likely be beneficial to everyone going forward:

-Programming (focus more on the logic and concepts as oppose to language specifics)

-experience with different OSs

-Specifics of how main components work internally

-Using the command line/terminal

-Basic Analog and Digital circuitry as it relates to computers

-Computer networking

-Photoshop

-CAD

But this is probably to much information for high schoolers, and can become very deep and dense. Again it all depends on how deep you want to go.