ICFP Metrics: The magic number

Teacher Contact Ratio

The proportion of the timetable cycle that teachers spend teaching classes, taken as an average across all teaching staff i.e. the proportion of teachers facing children at any point in the teaching cycle.

The calculation

TCR = total planned curriculum periods per cycle / total bought periods provided by every teacher

The ‘cycle’ being the number of lessons delivered with the regular weekly, bi-weekly or other planning of lesson delivery, the ‘total bought periods’ figure includes management time, PPA and surplus teaching periods: this represents the total capacity of the teaching staff (cycle x full time equivalent teachers).

In the primary phase, the following calculation is sometimes used:

TCR = total number of classes / full time equivalent number of teachers

This method assumes a single class per teacher is the delivery mechanism used across the whole school, which is rarely true in practice away from the primary phase.


When considered alone, there are some issues with the use of teacher contact ratio as a measurement of school structure that must be understood if it is being used to compare school structural efficiency. The magic number of 78% as part of the magnificent seven is not always so magic! From the previously stated target, recent indicators advise between 75 and 80%, although we have seen more in the 62-70% range than would be desired.

  1. The metric alone is not related to the size of the curriculum that is planned as it does not factor in any of the other measures, specifically average class size. Therefore, it is simply a percentage of the bought staff capacity facing learners without regard for the size of the curriculum planned. The curriculum that is larger than optimum for the current number of children in the school can still have a desired teacher contact ratio although it will cause the other metrics being out of line with norm indicators.
  2. Use if the magic number may assume a usefulness to a specific phase of education. In the primary phase (4-11 years) a class = a teacher, broadly, the achievement of the target contact ratio is often much more often successful. However, in the more granular nature of the secondary phase (11-19 years) it is often not achieved. With many more primary schools than secondary schools in the system using the average of schools make s this a blunt instrument for implementation.
  3. Does use of this measure imply or support the narrative that teachers are bought to teach without real understanding of what that involves in our modern education system? Teachers teach, therefore the majority of the bought resource should be used in face to face activity (be it online or in person.) This alone should be increasing the conversation about teacher wellbeing where the role of the teacher has administrative burdens that make the role increasingly burdensome and so where is the workable line to be drawn?
  4. The measure, for many, only discusses the teaching element of the role; “How many of the teaching staff are facing learners at any point in the school day?” We would do well to include in the narrative a discussion the use of the bought teacher capacity within the context of the school (some are more challenging than others) and how this capacity is used to the greatest effect. The metric narrative surely must be about all four aspects of teacher deployment: learner facing teaching; planning, preparation and assessment (and its enhancement above the legal minimum); leadership and management time; and training time. In addition to this, the levels of unassigned teaching capacity often poorly measured, articulated or costed. This often results in serious inequity in its distribution across a teaching staff body (particularly in the secondary phase) and creates difficulty and over burdening some staff more than others, often those who end up teaching the higher number of learners in a cycle in bigger classes impacting their ability to assess work meaningfully.

If the narrative involves all of these, then the discussion of school efficiency becomes stronger, context and purpose driven for the benefit of all learners and staff.