Computer Science dept saving £2300/year with Yacapaca

These are real numbers from a secondary school in England, that I got asked to work out this week. They are a fairly typical single-department customer for us; I don’t have permission to share the name of the school.


The figures are self-explanatory. Here are the assumptions that I made:

  1. If a test was not run on Yacapaca, it would instead be done on paper, using photocopies at a cost of 5p/copy. I sampled printable test online and found that 8-10 questions/sheet is the normal range, so took the larger figure.
  2. If a test was done on paper, it would take an average of 5s to mark each question. I’m quite certain I could not sustain that for a block of 20 questions x 30 students, but perhaps an experienced teacher could.
  3. If Yacapaca was not used, another test could be found in no more time than it takes to search Yacapaca for one that is suitable. No time was allowed for writing a test. On the other hand, I did not allow any time for authoring within Yacapaca and given that most teachers do some of their own authoring, this probably balances out.
  4. I took the average teacher salary from and added 13.8% NI employers’ contribution to get the ’employer cost’ of a teacher. If your salary is over £29k then the saving is commensurately greater.

And if you really want to dig down, here are exactly what the columns mean:

  1. Assignments/yr is assigned quiz attempts. Students*quizzes*attempts per quiz.
  2. Questions/quiz: the average number of questions in each quiz, as assigned, sampled from the last 50 assignments.
  3. Assigned questions: (1)*(2).
  4. Completion rate: not all students complete all questions.
  5. Completed questions: the marking calculation is based only on the number of answers given, not questions asked.
  6. Cost of photocopying saved: total quizzes * 5p. In reality, because quizzes are of different lengths, it’s impossible to get a good estimate without sitting over your photocopier. However, it’s reasonable to suppose that every quiz would require at least one copy, so I took that minimum value.
  7. Cost of marking: see the separate calculation in the table on the bottom right. A good question to ask yourself is this: if somebody offered to pay you to mark their tests for them, would you ask for more or less than 3.6p/response?

If your school uses Yacapaca and you want to show your SLT just how much you are saving, I’d be happy to plug your numbers into the same spreadsheet for you. Write to

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