Here in Japan they're doing Scratch and then roll into samples in 8 different languages (basically hello world with a loop and some variables) in middle school.
My son however did a scratch book when he was ~7 and did some Arduino programming in that Arduino flavoured C in a robotics course which he's still doing (he's 10), but we're doing some things together in C because of that. I had originally thought about Ruby (because I like it and it's clean) or Python (because there are tons of ways to use it for beginners, like MineCraft scripting), but he's handling C just fine.
Now, what would I recommend for a class of students? Honestly I'm not sure Scratch is better at getting the concepts of program flow than flow charts with stencil templates, I actually think flow charts would make more sense. Once they get the concept of variables and loops look for something simple and visual or something they know and can see immediate results, like that MineCraft and Python setup or maybe even go old school and grab that demo where you move the robot around. Just try not to do the whole think in Scratch, as I think that past a point forcing that visual representation is detrimental and could actually turn off some students who would be into actual programming.