Four sets (A, B, C & D) of mock exams (pairs of Paper 1 & Paper 2 exams) for both Maths SL and Maths HL are available on the Sample Mock Exams page (16 exams in all). These original mock exams do not contain any past IB exam questions. A markscheme / solution key is available for each exam.
New original specimen papers (SL & HL) will be appearing in the near future for the Analysis & Approaches course. These will appear on the new site, soon to be launched, for the Analysis & Approaches course.
There is a strong argument that the most important assessments - other than the official IB exams taken in May or November - are the mock exams (i.e. 'practice' exams) that students take 2 to 4 months before the IB exams.
There are essentially three ways to 'make' a mock exam. In order of difficulty - from least difficult to most difficult (in my opinion):
1. Use a full IB past exam.
2. Choose a selection of past IB exam questions from different years.
3. Write your own.
[or some combination of two or more of these approaches]
A subscription to this site offers a 4th option which may be the 'best' option - and that is using a sample mock exam written by me. It might be 'best' ... not because I have good skills and experience in contributing toward the writing of IB exams (which I do), but because there are significant weaknesses in the other three options listed above.
The biggest danger nowadays in using a full past IB exam question is that students have easy access over the internet to past IB exams going back many years. Thus, you may choose a past exam (one that you did not use with your students) as your mock exam without knowing that some, or all, of your students had obtained their own access to it (and the markscheme).
The same danger also applies to constructing a mock exam from a selection of past exam questions from different years. It is sometimes difficult to remember precisely which past exams you used with your students. It is also very difficult to organize questions from different years and get them to 'fit' together in a way which makes a good exam. It is not easy to get the right balance in terms of covering the breadth of the syllabus and arranging the questions in a suitable order from 'accessible' (i.e. easier) to 'discriminating' (i.e. harder) questions.
Writing your own mock exam can be a very worthwhile process. However, this is something rarely done by teachers because of the time and effort required. It also demands a certain depth of experience in teaching the course - and it would also be very beneficial to have had experience as a member of an IB exam writing team. And that's the last reason why it's very difficult to write a mock exam on your own - it's much better done by a team of people.
I have written some original SL and HL mock exams (including markschemes and suggested grade boundaries) for subscribers to this site. Although not a genuine 'team' effort, I did share these mock exams with other experienced IB teachers to check for suitability and accuracy.