Missing a month to go on a spring break party binge, or to play video games at home, or a number of other frivolous choices is an issue in my mind, but to miss classes to participate in WC or Olympics is a very different thing. There is a whole lot of learning that is happening and not just the athletic growth of these two players. While not ideal, illness and accident can cause students to miss significant time in class as well - how much better for them to be traveling and experiencing different cultures instead of being in a hospital.
I disagree that computer time is the same as class time - the interaction with teachers and fellow students is a large part of the learning process, but a dedicated student can afford to miss a month of that experience if they are diligently keeping up with the work on-line.