Depending on where you draw the line for millennials the school computers could have been running anything from Windows 95 to Windows XP. BASIC wouldn't have been included in XP or 2000, and depending on what exactly they were using, it may have been easier to use something with more features. QBasic for example wouldn't have syntax highlighting. Simple programs in languages like python or perl can be used to teach the same concepts, with fairly similar syntax, and would have been more applicable to software people were actually writing at the time.