Pity those poor kids can't be given an ARM system with a little more horsepower.
I like Pascal's idea, but unless he moves up to something like an A9 or A15, I'd favor the X86 version.
The Raspberry Pi comes in at £20, that price point is only possible due to the age of the technology involved.
The hardware is still rather powerful and should teach the children using it to optimise their software rather than simply using brute force to solve a problem.