How taxing will it be on a school's bandwidth if 18 tablets were to skype someone at the same time. It is my understanding that Skype uses 3-12kb/sec. We don't plan on using skype alot but were thinking of using it in conjunction with one lesson.
Last June I handed in my bachelor thesis about synchronous eTandem Language Learning at the University of Lucerne, Switzerland. During our school project we skyped once a week with a Scottish class around noon over a period of 10 weeks. The technical problems were enormous. The most we got out of our bandwidth were 8 simultaneous connections at the time. Before that, we tried vRoom by Elluminate and we had even more problems (with the firewall and the bandwidth). I believe that it is not possible to skype in a class setting. I will try it with small groups of 4-6 students.