Excellent article, IMHO ... re: grammatical range I wanted to suggest that complex adverbials and noun phrases as subjects / objects helps with being precise and ... (important) ... that is a teachable / learning thing that you can actually be learned.

I hope it's okay if I pitch in and suggest working only with real exam questions.  I've seen learners use questions from crappy, faux "How to get a 9 in all sub-skills in IELTS in just one hour using our amazing miraculous method" ... these faux Writing Task question are NOT formulated in the same that IELTS questions are (esp important for the data transfer Task 1 questions) ... I've seen some learners working with bad / wrong / weird graphs and it's difficult to practice Task Achievement on a writing task when you're working with poorly-worded fake questions.

Best article I've read on IELTS Writing!  Good luck, Emma.  I hope many students find their way to your sessions.  Writing takes time + a particular talent to teach, IMHO and it's a labour of love to correct, give meaningful feedback, organize all the exercises to develop the micro-skills, etc.  

the suggestions are really helpful and professional.

Thank you Andi. I'm glad that people are finding it useful.

To write an IELTs essay needs high skill in profound vocabuary, precise expression and intimate structure in English.

excellent article,really helpful,thx a lot Emma