The issue of scalability is not confined to cost considerations, but time as well. When I worked for the Qualifications and Curriculum Authority, my brief was looking at systems for assessing information and communications studies and computing. I visited one company with someone from the Department of Education. She really liked the system we’d seen. “Perhaps the Department could support that somehow.” I asked her what it was she liked about the product, and she replied that it would only take one minute to assess a pupil. I pointed out that that could scale up to one day a week.

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See also: The aggregation problem and The scalability problem (part 1)