For a modern mathematics education that is strongly oriented towards the individual learning and performance levels of children, fundamentally different structures of learning are required compared to before - both in grade-specific instruction and in mixed-age groups. The new teaching resource Flex and Flo has been developed specifically to address these challenges: The central element for the students' work consists of four thematic workbooks per school year, which the children can largely work on independently: two workbooks on arithmetic, one on geometry, and one on the topic of practical math and measurements. The central element for the teacher is the teacher's guide, which includes detailed instructions, photocopiable templates, and suggestions for further exercises to support individual development. In addition to classroom observation, the diagnostic workbooks are particularly important tools.