The following is the figure that captures this finding:
|Above copied from|
OECD (2015), "Indicator D2 What is the Student-Teacher Ratio and How Big are Classes?", inOECD, Education at a Glance 2015: OECD Indicators, OECD Publishing, Paris.
Extending the chart from OECD....
Add to this picture the widespread instances during which teachers are doing something else besides teaching to either augment their income or perform other assigned tasks, and the fact that instruction time has been cut short to accommodate multiple shifts, it is highly likely that only about half of the time inside classrooms is spent on teaching and learning.