This reminds me of how I started Redemption here at Oakdale Christian Academy. Several of the students were already playing Yu-Gi-Oh, and so I started playing Redemption with whoever wanted to play. Soon all the students switched games.
I would recommend that if you let them play Yu-Gi-Oh in your classroom after school that from the beginning that you also start teaching Redemption, and have that be the game that you play with students who want to. Over time, more and more students will switch because it's always more fun to get to beat the teacher.
As you have students who want to switch, contact Ken Locklin of 3LG. He used to have a policy that he would trade people Redemption cards for Yu-Gi-Oh cards or Pokemon cards (2 for 1 trade I think) as incentive to get people to switch games. If he still does that, then it would be a great way to get them started without costing them a ton. If he doesn't still do that deal, then talk to Schaef and see if he'll do that deal with Storehouse cards. My bet is that at least one of those guys would do it for you.