Ability grouping was a new concept to me, it sounds like the intent is to group similar students together so you can teach to their level. I have always done the opposite. I prefer to split the strong students equally into groups with students that may be struggling. I find when they work together the academically stronger students end up assisting te others with their learning. Kind of like having a tutor to support each group as I work my way through the class. There is so much more to the link and media below and I encourage you to take the time to explore it!