Fantastic guide!!!
I remember how preparing for JMSS mostly consisted of reading everything on the internet that mentions the test. I went on yahoo and the information provided was a bit vague; so it was hallelujah when i found IndefatigableLover's post. Nevertheless, this guide is useful on its own agenda and future applicants should definitely use it!!!
I agree with how youtube videos can be a valuable resource of preparation. If anyone has heard of the Vlogbrothers (John Green & Hank Green), they'll have heard of their latest channel called CrashCourse. In a nutshell, the channel covers important topics in history, biology, chemistry, physics and literature. I highly recommend watching these videos and many other science dedicated channels like Vsauce and SciShow. Reading books that explains scientific concepts are also great. Bill Bryson has written a novel called 'A Short History of Nearly Everything' which literally delivers information from atoms to how plane works. I think this will help with the Science Interest and Communication part of the exam. The book explains science in a very neat and succinct manner whilst providing examples to intensify the reader's understanding. In scientific essays, the ability to provide examples is a must-have skill!!! Other important aspects that will be considered are; grammar, spelling, use of scientific language (instead of 'shiny' we use the term 'lustrous') and a fluid structure - quite a fundamental convention in essay writing.
The Mathematics and Numerical Reasoning section was a reminiscent of the MHS/Mac.R test - but slightly harder. You cannot study for Numerical Reasoning but you can train yourself to be better by doing maths puzzles. Knowing your roots/square numbers is also a great asset for identifying numerical patterns. Mathematics contains questions of different topics in maths from year 8-10. Data analysis, trigs, parabolas, Pythagorus, algebraic arithmetics, linear, quadratics, surds and ect.
Science Reasoning ranged from reading scientific passages and applying them to questions; analysing data and answering questions and determining the correct answer to a basic science question (e.g. which is element is most reactive? a. oxygen b.sodium c.nitrogen d. iron e. none of them) This is one of those tests that are unpredictable because it's a concoction of different subjects melded into one. Reading and analytical skills are crucial and understanding basic science fundamentals is also important. My example question was one of the questions from this year's test. For me, this question was easy as I know that sodium is highly reactive when exposed to oxygen. Some people may have to do a little thinking - they could cancel oxygen and nitrogen out as they are nobel gases. Between Iron and Sodium, people could take an educated guess and pick sodium.
An important thing to keep in mind is that selective entry tests are aptitude tests. It's designed so you can't 100% prepare for it and JMSS specifically made it to filter out; those who really love science from those who only wants to get accepted because it's a selective entry school.
Lastly, the test is not overly difficult and people shouldn't stress much about it. There are going to be 'those' questions that'll induce a moment of mental blank, but overall; if you know the maths and science that is required at your year level, then you're good to go.