I have to ask - have either of you had kids and been at poverty level? Worked part-time jobs that were your sole source of income? Worked "temp" jobs for which you could be fired literally from one minute to the next because the employer is a third party and has no obligation to keep someone on that they feel can't be there 100% of the time?
I have. And while I certainly did the best I could to keep my child away from other kids if she was ill, if it meant losing my job, it could not be done. Maybe that's not the situation here but to generalize that all parents have the capability to just whip up someone who will watch their child while they go to work to try to keep food on the table and clothes on their kids... Not everyone has a neighbour, parent, sibling who can take care of a child during such times. And trust me, if you are the bread-winner and at risk of losing employment (or not getting future employment) you will do what is best for your family in the long run.
I'm also a biologist (obviously, I'm no longer in the above situation but I am certainly sensitive to it.) How does that apply? Well, IMO, we are entirely too paranoid of bugs. Yes, everyone is miserable for a while. But it is childhood illness (to a degree) which builds our immunity. My folks tried to spare my niece from any childhood illness for several years by keeping her out of daycare. When she was ready to go to school - suddenly she was catching all the bugs that most catch at younger ages in daycare. The end result was a lot of missed school, poor grades, and probably much more strain on my parents (yes, they were grandparents raising her) than they might have experienced had they allowed the natural course of childhood illnesses which can not be vaccinated against such as colds and flus.
I certainly can sympathize with the teacher's POV on this. But I think it wise to keep in mind that there is an amazing number of parents out there who quite simply do not have the resources that many educators think they should have. Again, that may not be the case here because it's a specialized class.
just presenting a different POV. KCat