Java is covered by android and C is covered by jailbroken iDevices. PHP you can do on both, I guess (at least you
can on ios (and
here's some more, so you stop trying to troll me about that.
Now you said:
"Un-jailbroken iOS not so much, as its strict W^X policy and App Store Review Guidelines make on-device compilers impossible."
And, while technically correct for the jailed devices (not counting the stuff, where you need to be online), you ignored the availability of interpreted languages (most of them turing-complete) on iDevices, which, suddenly, are the only ones available.
So, why don't you ask that teacher from TFA to VB your $200 pee-cees a Winblows app that takes them on a trip to somewhere damp and dark together with the toolchain, as they're evidently unnecessary to teach kids programming these days?
Admittedly, I have no idea what to tell you about the kids, who don't own a smartphone, but have a console, apparently they're his target audience. Maybe he should create an account on MS Zone (or however it's called these days) and try to upsell them VB there. I wish him luck! He'll need it. ;)