The participation rate is the percentage of children who have been measured in mainstream state-maintained schools out of those eligible for measurement (this excludes children who could not be measured due to physical or mental impairment).
The overall national rate has increased from 80% in 2006/07 to 95% in 2018/19.
The participation rate can affect the accuracy of estimates derived from the data. For example, if the participation rate is very low in a local authority then the prevalence estimates for the BMI categories should be treated with caution as those children measured may not be representative of all children in the LA. See annex B of the appendices for more detail.