Students ages 11 to 16 are commonly enrolled in the Middle Years Program (MYP) or Key Stages 3-4. The former is delivered by the International Baccalaureate Organization (IBO), and is employed in many countries. In contrast, Key Stages are the basic levels of formal secondary education in United Kingdom (except for Scotland). Both are fundamental regarding the mathematical education of students, as they introduce many basic notions to deepen their understanding in order not to carry forward misconceptions to the ensuing levels. One of the biggest challenges tutors encounter is helping students to do away with what they have already learned incorrectly, and replace the same with accurate knowledge.
I was initially engaged with MYP and Key Stages 3-4 mathematics mainly when the siblings of my older students asked me for help. Since then, I have invested a lot of time in studying the corresponding mathematics syllabi to became fully conversant. Furthermore, due to my extended educational network, I have many active subscriptions to mathematical coursebooks for those levels which is extremely useful for my students, as the majority of those books are not sold individually.