Complex sentence: The school also offers more challenging optional overseas expeditions for older students, such as the students have walked the Inca Trail, climbed in the Himalayas and built play areas for the children of Indian and African villages.
Split into simpler sentences: The school also offers more challenging optional overseas expeditions for older students. These have include walking the Inca Trail, climbing in the Himalayas and building play areas for the children of Indian and African villages.