The purspose of this study is to investigate how teachers are working to individualize mathemathics education relative to high-performing students and how they define the therm individualization. According to the Swedish curriculum the teaching process should be based on the students prevoius knowledge and experiences. The teachers should in their preperation take every student in to consideration. To be able to investigate these subjets I prepared following questions: What does the concept of individualization in mathematics mean for the teachers? What does it mean to work with an individualized mathematics teaching? How does teachers individualizes teaching mathematics relative to high performing students? This study is based on a qualitative method with both interviews and observations. The theoratical approaches I have used refers to the term invidualization and how to implement an idvidualized education in matematics to stimulate high-performing students. The results of the study shows that invidualization is a complex concept and for the teachers it is about finding out the students level of development to be able to give them tasks at a level which is challenging. The high-performing student either gets more advanced tasks or get paired up with other high-performing students where they get to solve problems at a level which is challenging.