While bash has a "better" language than CMD.EXE, just about any shell language can be used as a first stab at sequencing, looping, and branching.
Even a few lessons on the shell can give students something they can begin using right away, since it is built into the system. Since the shell is installed by default, you can get to work right away, without a download and install -- often illegal on lab machines anyway.
I can recommend A+ texts (even out-of-date ones) since the focus on the right set of topics, albeit in more detail than you probably want.
Get your lab to install Cold Storage so you can have students change settings, find and install software packages, whether admin tools, languages, or something like installing Ubuntu within a file on a FAT partition.