FSiM

First Steps in Mathematics helps teachers see mathematics through the eyes of a learner. It is a research-based diagnostic framework that:

• Describes the developmental phases all students pass through as they learn mathematics
• Includes validated diagnostic tasks that accurately identify student progress
• Outlines learning activities that target developmental triggers proven to advance student learning
• Links assessment, teaching, and learning
• Enhances differentiated instruction within an effective mathematics classroom

Strands include:

1. Number Sense* and Early Algebra
2. Measurement
3. Geometry and Space
4. Data Management and Probability

(From Pearson Canada's website) 

 Here are some places to find out more about the program:  

Steps PD (Developed the FSiM Program)

Pearson Canada (Canadian Publisher of FSiM)

Here are two excellent sights for more FSiM resources: 

The Western Australian Department of Education has some excellent comprehensive resources, including the Number diagnostic tasks, Measurement, Geometry and Space, and Data Management and Probability Resources. 
School District 71 has some very practical resources for using FSiM in the classroom.