An Educational Programming Language should not be too far removed from mainstream "Industry" languages. Complexity should not be completely hidden while teaching/learning Programming but must be gradually unveiled.

I believe a multiparadigm language with a small "kernel language" to which you progressively add more layers for different paradigms should be the way to teach. The Mozart/Oz language i think shows the way - https://en.wikipedia.org/wiki/Oz_(programming_language)