depends on what kind of project (quilting,piecing) etc you are gonna do in class. If just straight piecing then a simple machine will do. If machine applique then the same except one that has zig zag. However, if class in machine quilting, it is best to have your larger machine as the smalle ones don't give good results.
But whichever you take besure you know its ins and outs. take the manual and all accessories needed. Ive had students come to class without the plate that covers the bobbin. Also the extension table. Too many arrive at class without all they need to do the projects. I've had students come to class without the necessary walking foot and say they thought they would try it before buying the foot.......