New Zealand Post Primary Teachers' Association / Te Wehengarua (PPTA) guide to calculating average class size.
Average class size calculation guide
Some timetabling programmes used by schools have a function which calculates average class size in a way that does not meet requirements for Secondary Teachers' Collective Agreement (STCA) purposes and can give an erroneous average.
This is most likely where the periods are of varying length.
If you believe that your class size average is not what is indicated by the timetable programme then the correct way to calculate it and check the accuracy of the figure is:
- Find the weighted contact time for each class (roll times the number of minutes you have that class each cycle)
- Add the weighted contact times together.
- Divide the total by the number of minutes you are timetabled to teach each cycle.
Calculating individual average class size (xls spreadsheet)
Here is an example for a teacher in a school with a 5 day cycle. The teacher has 5 classes and sees each of them 4 times for varying period lengths.
(NB. Form classes do not count for the average class size unless the form time is part of timetabled contact time.)
|
Timetabled classes |
Number on class roll |
Length of contact periods with class (minutes) |
|
||||
|
1 |
2 |
3 |
4 |
Total |
Weighted contact |
||
|
1 |
25 |
60 |
60 |
60 |
50 |
230 |
25*230 = 5750 |
|
2 |
22 |
60 |
45 |
50 |
50 |
205 |
22*205 = 4510 |
|
3 |
32 |
60 |
60 |
60 |
50 |
230 |
32* 230 = 7360 |
|
4 |
25 |
60 |
60 |
60 |
50 |
230 |
25*230 = 5750 |
|
5 |
26 |
60 |
50 |
60 |
50 |
220 |
26*220 = 5720 |
Weighted contact total = 5750+4510+7360+5750+5720 = 29090
Total contact time = 230+205+230+230+220 = 1115 minutes
Average class size = 29950/1125 = 26.09.
At this level the school and the teacher would need to agree an appropriate compensatory mechanism as the individual average class size of 26 is exceeded.
Some school timetable programmes would incorrectly calculate this teacher’s average class size as 26.00 and the school would therefore be unaware (unless the teacher corrects it) that a compensatory mechanism is due.
Calculating individual average class size (xls spreadsheet)
How should average class size be calculated? (2008)
Class size policy statements (2007) Non-contact time, average class size and timetable policies (2011) Also known as "About Time" Non-contact time, average class size and timetable policies (2011) Also known as "About Time" Timetable Policy example 1 (2008) Timetable Policy example 2 (2008) Timetable Policy example 3 (Area School) (2008) The meaning of 'endeavour' and 'consultation' (2008) Class size in New Zealand secondary and area schools 2011
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