Numeracy Ninjas is a whole school numeracy intervention designed to fill gaps in students’ basic mental calculation strategies and also to empower them with the numeracy skills and fluency required to progress to and achieve success in Junior maths concepts . Furthermore, through the incorporation of Science of Learning principles such as retrieval, spacing and interleaving, it ensures that students’ learning is retained over time and transferrable to many different contexts. There are different booklets based on the time that the students have over the duration of the term to complete each course. It comprises a 5 minute skills test to complete in each lesson which includes: 10 questions on mental numeracy calculation strategies, 10 timestables questions and 10 questions on key topics that must be mastered before progressing to JC Mathematics. As well as this, it contains a 'belt system' where students compete to achieve their black belt. Numeracy Ninja boasts that their "little-and-often approach, in combination with a research-informed design, which systematically plans the revisiting of skills, ensures students’ improved numeracy skills and fluency are retained over time".