>distributable and saleable software
Do you or they make the Python code into an EXE for sale, using one of the available tools, or sell as source?
They also offer free teacher and student accounts with the ability to limit time. Can't say enough positive things about the service.
Python is dead simple—I recently had to take on a project written in it having never programmed in Python before and I essentially did not have to learn it to get the feature done.
I might give Python an edge for a number of reasons (a shell is a simpler environment than a browser in a number of ways, some of the language features are cleaner), but to say that it's much harder doesn't bear out with my experience. Capable first-timers become productive at about the same rate.
I've found it's mostly experienced developers who trip over JavaScript, because they're carrying a set of expectations and are weirded out when it does something different. Turns out principle of least surprise means different things depending on people's backgrounds.
Feel free to choose to start someone with Python if you prefer it, or if they're likely to want to work in a domain where it makes sense (say, data science), but it's probably not going to change your learn-to-code outcomes much.
Comparatively, other languages, like Python, will throw sane exceptions and a meaningful stack trace when something goes wrong.
I have the kids learn Python between age 9 and 11 depending on when they are interested. We write games and learn the fundamentals of CS by following the curriculum of Rice's "Introduction to Interactive Programming in Python" class designed by Rixner and Warren. It has a Python interpreter and game library that compiles in-browser into javascript, which is a very helpful design for a first class, and for sharing their results with myself, their families, and each other.
Afterwards I encourage those who really enjoy it to learn Java, also using web sources primarily. I intercede when they are stuck but generally they help each other out.
Some of them used to use the Java to write Minecraft mods but that has become a bit more tricky.
There was one student who started to learn Java at age 7, but in general that's too young. If you push things too earlier they don't get a head start. They get burned out and don't want to have anything to do with it any more. You really need to be sensitive to what they are interested in and let them lead.
Most kids when they see others making their own games want to try their own hand at it themselves, so I have managed to create a self-perpetuating cycle.
Learning languages to make games makes sense. Pushing languages to force concepts will be resisted and is counterproductive.
The games approach is nice too because they rapidly learn trigonometry, basic physics, and linear algebra by age 10 or so, and are teaching themselves Calculus on Khan Academy by age 12, as well as researching optics, writing their own shaders and generally doing what most would consider college or graduate level mathematics. Their Java skills also often lead to writing for Android. Some selling their games and other software at a certain point, which helps their families.
It helps that on the reservation I have a great deal of autonomy in what I can do. I've worked in public outside schools before. None of this would be allowed there.
I don't really care for the idea of dumbed down toy languages that can't really be used for production software. Python and Java are well designed enough that they are understandable and usable from the age where they are able to do programming thought. Python is a simpler one to read and use and so we start with that. But Java is very similar and the lessons of Python directly transfer. Java ends up being much more useful for distributable and saleable software, though it is harder as a first language.