Dear Grimsim,
Depending on how much time you have and what their initial level is I �d definitely adopt some cousebook. IELTS comes in 3 variations ACADEMIC, GENERAL TRAINING and LIFE SKILLS, from your description it seems that you �d be interested in the first variant. The speaking and listeining is the same for Academics and Generals (Life Skills is completely different) and UNLIKE other Cambridge tests students listen to it ONCE only - so they need some adjusting to it and training. Both listening and reading parts are set in a way that they are getting progressively more and more difficult. Being quite young, your students may find the final texts and listening parts (which are e.g. academic lectures) quite challenging.
For the speaking test, definitely look at youtube and write IELTS OFFICIAL where you are going to find lots of candidates with ACTUAL grades they got for speaking including a commentary why they were awarded these. That should give you a hint of what is expected and how your students are going to fare.
Bookwise: I �d look at New Insight into IELTS (for both General and Academic), Action Plan for IELTS (shorter), Step up to IELTS by Cambridge University Press; Headway Academic Skills (low starting level of students, so I �m hesitant if it makes sense because most academic institutions accept candidates with bands 6,5 and above), IELTS Masterclass (for Academics - may be your best shot, check) by Oxford University Press. Macmillan has a variety of books which don �t specify neither the kind of IELTS they are preparing for (and there are e.g. significant differences in the types of texts students are expected to produce in General and Academic IELTS) or the starting level of the students which personally I don �t like. These are books like Direct to IELTS, Ready for IELTS and Focusing on IELTS. The one that is worth having a look at is IELTS GRADUATION (for Academics).
Of course there are also testbanks - I �d try to choose the ones with as many Academic (or perhaps solely Academic) as possible.
If I can help any further, write me a PM :-)
best of luck,
joanna :-)
