Harvard’s introductory-level computer science course, CS50, teaches Scratch for the first week. The course then uses Scratch like pseudocode to outline the high-level structure of programs for students to write in C. This is a proof of concept that Scratch can be part of a good introduction to programming, though the introductory coursework I took at university went straight to learning with Python instead of with Scratch.

For teaching a child, it depends on the person’s interests. You can’t go wrong with Scratch (it looks fun, it’s easy to start with, and it’s immediately accessible within a browser), but the child might eventually want to move on to a more flexible language like Python for more complicated programs.