Well, I believe none of us saw that one coming. I was extremely disappointed when I heard the news because I know there is not much chance of my kids doing well for this one. While the complicated format is an issue on its own, the more pressing matter I believe is the fact that even the best of us can have problems writing a proper formal letter using the proper language.
Nevertheless, I am glad that a couple of weeks prior to the exam, I did give out some samples of formal letters. Although I only went through them briefly, hopefully some of it stuck with my kids and helped them during the exam.
In any case, here are the samples that I gave out to my students. (It is a little late but it can serve as reference for next year? HAHA)
In my opinion, formal letters at this level are limited to only a few typical scenario such as a letter to request for permission, a letter to invite someone to an event or a letter of complaint. Each of these letters has a different purpose and it is reflected in the title of the letter (highlighted in red). The purpose is then reiterated in the first paragraph (highlighted in yellow) but in a complete sentence and sometimes with more details [Sample 2].
As can be seen from the samples, different purposes are expressed in different ways so it is important for your students to be able to produce these sentences. With average students, your best bet would be for them to memorise the sentences and alter them according to the question. Finally, formal letters should end appropriately (highlighted in green) according to the purpose of the letter.