I have to agree with both Krellin and Jimgov as far as doing this FTF. This site is great, but it's not appropriate for high school students- and you can get in trouble for leading them here. On top of that, FTF allows more control from your end, as may be necessary to take moves and apply questions to them with visual aid (ie Germany moved to Burgundy in Spring 1901 and bounced France who made the same move. What if France had used support in Marseilles?)
I support the idea of using the game in an IR class because the gain for certain learners is substantial while there is little negative effect. I don't think this game would turn anyone who is already in the class off to the topic. I would definitely analyze every move, though, and possibly create a larger map to accommodate each student with a country. World Map (eliminating certain countries, adding SC's, etc.) may be better, though more time would need to be dedicated to communication. It depends how often the class meets and what you actually have to get through.
Someone mentioned generals and PM's. As far as that idea goes, I would steer against having the generals become adversaries. Instead, I would advise the PM's to conduct diplomacy while the generals of the same country talk to each other to formulate an attack strategy. Perhaps even swap positions every year. I think that is far more effective because the generals have to deal with the diplomacy of the PM. Though they're all on the same team, it shows how even people who have the same goal can come into conflict (it makes sense to attack Germany strategically, but diplomatically, the PM feels that Germany is more likely to aid their country and should be kept around for that).
All my opinion. I'm not a teacher, but have some type of experience teaching and as a school board member.