Sadly a converter doesn't exist from VX Ace to VX. Your best bet is to see if the teacher will install VX Ace on the computer temporarily. Otherwise, google "how to portablize software" and see if you can do it yourself. Now a converter for VX Ace to VX probably won't exist for various reasons. VX Ace has an entirely different new engine. New data structure, new event commands, new way of handling maps and tilesets. It'd be far too much work to try and convert that all to VX without running into complications.