One class of third-graders who live on the Atrai River numbers 29, and the boat is both classroom and school bus-equivalent, picking up and dropping off students, while in between giving them classroom instruction for the day. That instruction includes low-tech and high-tech presentations. A standard-issue blackboard features prominently in some lessons; other lessons involve a solar-powered computer that has Internet access. Students sitting on wooden chairs write with pens and pencils on pads of paper that rest on wooden benches.

The boats themselves are modeled after a noka, a traditional Bangladeshi wooden boat. The floating classrooms are 50 feet long and 10 feet wide and have arched metal beams that run around the frame, rather than columns in the center of the boat that would interfere with the students' line of sight to the teacher. In addition, the roof is weatherproof, built to withstand the annual monsoon rains.

Annual costs for running one floating school, including teacher salary, is $6,500. The more than 200 members of staff includes dozens of teachers and dozens of boat drivers. Volunteers number more than 300. The national Education Department, which with the boats are registered, provides free materials for students in Grades 3 and 4.

The floating classroom attempts to solve the problem of how to educate students in flood-prone areas. By some estimates, particularly heavy monsoons can sometimes put up to 70 percent of the country under water.

The boats run six days a week, year-round, with each day consisting of three sessions, each for a different group of students. In addition to the focus on elementary school students, some sessions are for secondary school students. The program also provides solar lanterns for students to take home, to help with homework.

A nonprofit group called Shidhulai Swanirvar Sangstha runs 23 floating schools in the northwest part of the country. The group's founder, Mohammed Rezwan (right), is a native of the area and began his project in 2002 with one schoolboat. A 2013 report estimated that the floating schools had reached more than 20,000 students in the then-11 years of floating education. A new report has that number at nearly 70,000.

The nonprofit also operates floating medical clinics, libraries, and adult education centers. Programs on offer for adults include practical instruction such as techniques for growing flood-resistant crops and controlling pests that plague the country's agriculture areas. In addition, some boats are moored in villages at night and employ a sail-based "projector" to show education videos on topics such as nutrition, hygiene, and children's and women's rights.

None of the students, library patrons, or medical patients pays a thing. Funding comes from individual donors and from groups in Bangladesh and in other countries. A part of that funding came in the form of a $1 million Access to Learning Award in 2005 from the Bill and Melinda Gates Foundation. Other funding has come from the Global Fund for Children ($5,000) and from the Levi's Foundation ($100,000), which has factories in Bangladesh. Recognition in the form of prizes has come from the World Innovation Summit for Education, which also donated $20,000.

Other countries, such as Cambodia, Colombia, and Nigeria, have or have had floating schools, but those are stationary. Floating education projects in Indonesia bring education to land-based students.