One thing I notice was missing in this write up is the software that the Raspberry Pis are running. The students are learning programming using MIT's Scratch platform (https://scratch.mit.edu/) and are learning numeracy, math, and science using KA Lite (https://learningequality.org/ka-lite/) a platform designed to give offline access to Khan Academy exercises and videos, in an environment that provides some of the motivational features and coach reporting tools that Khan Academy has available for teachers. Both of these tools are free and open source.
(Note: I am one of the developers of the KA Lite platform and part of the organisation that develops and maintains it, Learning Equality).
KA Lite is also currently evolving into a broader platform for content distribution, with a deployment to provide customized teacher training materials in South Sudan (through War Child, and again UNICEF).