I would stay away from a model named "Class", it is a keyword of php and it may will (as pointed by @AD7six) cause trouble if instantiated like that.
You can do the following:
class MyClass extends AppModel {
public $useTable = 'classes';
}
Be sure that the controller ClassesController calls MyClass
(with $uses
), but besides that, you can use the model like any other model without worrying about reserved keywords.