leneia, I agree it was appropriate for the school staff to be cautious. If there had been a toxic substance in the sauerkraut, children could have been harmed and we would not likely be joking about the incident now.
This article has a little more information than the previous one.
... Staff were concerned that the spoiled food could potentially cause a botulism outbreak and therefore the school was evacuated and the hazardous material unit was called to investigate.... The contents were examined and it was determined that the can contained sauerkraut which had been fermenting for a number of years.
Once it was determined that an outbreak of botulism had not occurred, students returned to their classes but were dismissed early from school....