I don't think just adding a board is going to help much. Academy went through several iterations of board size before it was settled on the One Zone as superior and it was mostly due to the fact that whoever moved first lost. That is not the lesson you want your burgeoning Mage Warriors to learn.
One of the extremely important things to learn about movement and tactics in the Arena is how to use various movement spells and abilities. Therefore, I suggest one of two courses of action:
1) Allow a select few movement altering spells and creatures to be added to your Academy spell books on the 2x3 board. Perhaps one or two "fast" creatures ([mwcard=MW1C04]Bitterwood Fox[/mwcard], [mwcard=MW1C05]Blue Gremlin[/mwcard]) and a [mwcard=MW1I12]Force Push[/mwcard] or two as well as a [mwcard=MW1A09]Jet Stream[/mwcard] or a [mwcard=MWSTX1CKA01]Surging Wave[/mwcard].
2) Jump into full blown Apprentice Mode. You'll almost only have the movement to teach and you can kick start finding fun new combinations with all of the Arena cards.
Obviously you know your players better than I do, but I would definitely suggest at least adding some movement cards when you expand the board.
