The most likely reason for not being able to publish the results of the study at this point is:
The study was biased, based on the fact that the test group was only from one school, and there was no control group.
Reason for rejection of papers
Scientific journals want studies to be done well and follow the right methods. In this situation, the scientists' study had some restrictions that could cause unfair results.
First, the study was only done at one school in South Florida. This means that the results only apply to a certain area and might not be true for other places or different weather conditions.
The results may not apply to a wide range of people because the group studied was not diverse.
Also, the study did not have a group for comparison. A control group is a group that is not given the treatment or exposure being tested in an experiment, so that scientists can see the difference it makes.
In this situation, it's important to have a group of students for comparison to see if the illness rate is different in schools with different temperatures. It's hard to prove that getting sick is caused by cold weather without a group for comparison.