Another couple of pupils complained they felt unwell, then a few more, and soon Royston high school's 627 roll were toppling like dominos: 32 pupils were taken to hospital, and the school was evacuated.
The cause? A rare - and highly infectious - outbreak of "epidemic hysteria", according to medical specialists. And in this silly season, mass hysteria seemed to break out everywhere about "the teachers that stole Christmas".
In Sutton Coldfield, a supply teacher received her marching orders after telling her nine-year-old pupils that there was no Santa: "All of you are old enough to know there is no Father Christmas or fairies," she told them.
The tabloids were "disgusted" that a teacher would shatter young children's illusions; we were surprised a teacher could now be sent on their way for telling the truth.
In Norwich, a primary school was publicly attacked for replacing its annual nativity play with a multicultural show.
Even Gordon Brown, the Chancellor, was infected. Speaking to a meeting of Muslims and Hindus, he attacked the Sure Start playgroups in Sheffield and London for replacing Christmas parties with "winter celebrations".
Is the celebration of other long-standing cultural traditions, as well as Christmas, really cause for such mass hysteria?
The Sun seemed to think so - to the extent that it castigated as "racially divisive" Haringey council's annual awards ceremony for high achieving African students.
It is ironic that in the same week that schools were being accused by the tabloids of favouring ethnic and religious minorities, a leaked Department for Education and Skills report should accuse them of "systematic racial discrimination". It seems that sometimes, you just can't win.