The last time I taught the high school "web development" class, I struggled with the resources available to me. The school didn't have space to host student work; the Chromebooks available didn't come with a text editor (a goddamned text editor! The most basic editor on the system is RTF!); the Chromebooks had also had Page Inspector disabled, which has to be the silliest administrative decision ever made. There is literally nothing malicious you can do with the Page Inspector. I can only imagine that it was diabled to prevent kids from learning how the web works.
Late in the quaterly cycle I started to teach a little Javascript, and for that I remembered JS Fiddle. Since it has working HTML and CSS panes, this time I started with it.
That made a huge difference. By the end of the very first class most of my students were monkeying around with CSS and HTML, moving things around, changing color, scaling text. I'm going to have to up my game if I'm going to have enough material for these kids even with one week less than last quarter.
It's still very limited as a debugging tool; without Page Inspector we're either going to have create our own debugging windows or spew message to alert(), which is never any fun at all. That's old school debugging. But it's really better than nothing, and it makes teaching programming possible even at the high school level.