Honestly it is better to set up an AS maths 2016 thread in the maths forums than setup a group chat.
It is easier to keep track of a thread and its also easier to go back and check older posts. If someone gets stuck on the same question as someone else did, you could just link the help post to that person rather than scrolling up like crazy or explaining it again. The OP could contain useful links too, and with a thread a lot more people can join including those teachers on the maths forums.