The New York Times has a forum discussing when children should be taught programming.

http://www.nytimes.com/roomfordebate/2014/05/12/teaching-code-in-the-classroom
Computing in the Classroom
MAY 13, 2014

following up on the article

http://www.nytimes.com/2014/05/11/us/reading-writing-arithmetic-and-lately-coding.html
Reading, Writing, Arithmetic, and Lately, Coding
By MATT RICHTEL
MAY 10, 2014

Jonah Sinick did the service of collecting previous forum threads on programming at

http://giftedissues.davidsongifted....5425/Davidson_forum_threads_on_prog.html
Davidson forum threads on programming resources

I am neutral about teaching programming in elementary school. There are more basic and important things to learn. But students in middle school who have the ability to learn algebra and other abstractions may also be ready to learn programming. Several algebra textbooks have computer programming exercises presented in BASIC, which is no longer pre-installed on IBM PCs, although many versions of BASIC can be downloaded. I think supplementing algebra with exercises in a modern language like Python is a good idea.