If the parents can't afford to send them to school and they need the child to work, then what about helping the child learn while working. Imagine a bullet proof MP3 player with two batteries (one charged by day by solar power while the other one is in use), gets new lessons continually pushed to it via highly redundant FM data broadcast at night. (Local transmitter can cover many villages, child can see from LED whether nighttime data receiving location has good enough signal). Several days a week the child could work for the parents while also listening to the lessons. Unlike with a radio, the lessons can be paused, rewound, postponed till convenient time etc. Only need good reception at night (when not moving around) Then maybe one day a week the child would come into "real" school and do more hands on stuff etc, put what they'd learnt into practice.