Having learned Python, then C++, then JavaScript, then C, then Java, I have to say Java is probably at the sweet spot; it strikes a good balance between providing enough conveniences over C and C++ to help avoid frustrating a programmer (garbage collection, no need to use pointers explicitly) without encouraging total carelessness like Python and JS do (inadvertently) with their lack of built-in static typing.

With that said, if you want to provide instant gratification and therefore encourage a beginning programmer to keep learning, Python and JS may be the best for introductory classes.

MIT's approach of using Python to do a one-semester survey of CS and Data Science, then using Java to teach serious Software Engineering, appears to be an effective compromise (I did three of their CS courses on edX).