We took a guided tour of the S/V Concordia, a school-on-a-ship for 11th and 12th graders (only 48 are accepted each year, and there are seven teachers on board, so the student-to-teacher ratio is excellent). The ship sails to over 43 destinations over a 10-month school year, and the students learn about much more than just academics (it's a university prep program) and sailing on a modern tall ship (they have to work as part of the crew). The tuition is 27,500 Euros, or about $100 per day. All things considered, this is a relative bargain. More info here.