I have a high schooler who is interested in coding, and a middle schooler who is interested in graphic design. While I was browsing potential programs for them, I found out about Microsoft Virtual Academy, a place for learning coding for computers and for games (Microsoft owns Windows and X Box, after all).
Courses are divided into areas of interest such as: game development, database development, web development, etc.
The courses that I browsed were split into several learning modules, clearly marked for time needed, and were delivered via video. The courses are free, and membership (or sign-in) is not required.
See if this is a good fit for your high schooler, college kid, or for yourself, at Microsoft Virtual Academy.