Good default setttings ...
....from the commentards; "I bet it's a result of outsourcing", "developer's fault", "change management's fault", etc. come up with something a bit more original please ! You don't re-develop an admissions system each year for the next pupil cohort, chances are it's been stable and unchanged for some time with no development "go-live" needed in recent months or years.
My money is on a human mistake in the non-outsourced admissions team accidentally pressing the "send the results now" button without realising what the effect was.