Stay with a Nepali host family, trek through the Himalayas, and volunteer at the village of Jitpur, 30 minutes outside of Kathmandu. The teachers at the school here themselves don't have much education & you can help them by creating lesson plans, coaching them & improving their skills. You can work with pre K unto secondary school. Keep in mind, there is no heat or electricity in the classrooms, but the kids are eager to learn.
Cost for these programs are approx $150/ week & are coordinated through the nonprofit, Volunteers Initiative Nepal (VIN).