On 'THE INTERNET' …
Many schools, at least in the United States, now use chrome as a
default, which is arguably better than IE. The issue is beyond just
security. Having a standardized browser allows schools to use
extensions, and plugins for more enriching educational content; It
also ensures that the content that was guaranteed to show up
identically on (almost) all devices. Also having a single system makes
troubleshooting issues much easier for both teachers in the classroom
and underfunded IT departments.

On 'REDUCING HARDWARE COST' …
In fact, many schools in the United States have adopted to use
Chromebooks for the cheap(er) price. Most applications used in
classrooms are web-based meaning having a lower-power device is
A-okay.

On 'SECURITY' …
Agreed. Although, sometimes it is not the IT Department which makes
those terrible choices. It's the higher-ups who think 'new stuff=cool'
without understanding it.

On 'WHAT ABOUT THE "JOB MARKET"'…
I'm not sure if open-source programs will become the standard for
businesses. Some businesses are quite reluctant to change (more so
than schools are). They'd have to re-train their entire staff to use
new tools, and sometimes re-tool their entire system/infrastructure.
And I'm sure every office worker is eager to learn a new computer
skill /s.

While Open-source software like LibreOffice shares many similarities
with say Microsoft Word, to a non-techie making the transition can be
rather difficult.

On 'LOOKING UNDER THE HOOD'…
I doubt many schools would, or could for that matter, do this.
Teachers are busy trying to get through teaching requirements as is.
They're not going to spend time looking through the source code.
Students are (unfortunately) either uninterested, or if they are,
they're already doing it in their free time.

-- Shinwoo Kim