Kano's Raspberry Pi kit is a bit of a crowd favourite, even though it clock in a bit on the expensive side. The bright orange colours combined with the custom operating system built for learning makes it appealing for kids learning to code.
Now, they have updated their OS to work on the much cheaper new Raspberry Pi Zero.
The operating system works pretty the same as before, packing in tons of different education programs in so kids can learn all kinds of things about electronics and coding. But this version's made especially for the Zero, so it will run well even though the Zero's pint-sized by comparison. It's worth checking out if you have kids you're teaching to code, and you don't need the full Kano kit to make use of the operating system.