Investigate student fares available from www.studentuniverse.com and www.statravel.com. Also take a look at consolidator airfares, www.dohop.com is a good search engine for those but there are others too. You should be able to secure better than the published fares available through regular retail chancels (including those listed on ITA Matrix.

Student Universe allows purchase of one-way fares ex-USA and later purchase of return air fare from same or different country and one needed travel on a Student Universe outbound ticket to get them to write a return ticket, just provide the outbound ticket number regardless of where it was purchased.