Yes and no. While the specific defusing behaviors we discuss here and in my books work across sectors -- in government, education and in the corporate context, there is one significant difference between dealing with angry parents, and dealing with angry clientele in other settings.
The Big Difference When Dealing With Upset Parents
In the corporate world, (that is, the for profit world), customers are important because, in effect, they pay the bills. While parents are taxpayers that support public schools, their importance is different. For a school, or teacher to be most effective, it's necessary to build a PARTNERSHIP relationship with parents, rather than a "transactional" relationship. That's because neither parents or teachers can solve the various educational challenges that come with each child.
So, there is an inter-dependence here. Teachers need the cooperation of parents to best fulful their mandates, which is the education of the children. That level of inter-dependence doesn't exist in the corporate world.
Implications When Dealing With Upset Parents
While no for profit business wants to lose a customer due to their anger, the implications of "losing" a parent are much more important. When an educator loses the cooperation of a parent, it's the CHILD that suffers. A non-cooperative or actively resistant parent limits the teacher's ability to do his or her job, but the outcomes have nothing to do with money, as is the case in the commercial sector.
The loss acrues to the child. It's the student who may suffer the impact, not only in the present, but far into the future, and that's the major difference. This potentially adverse impact means that while the techniques on this site for defusing angry customers/people work across contexts, the emphasis changes. It's far more important to use techniques to build bridges with parents, than it is to use those same techniques with for profit customers. So, one might work harder of being bilateral with parents than one might with a McDonald's customer. A teacher probably should focus on keeping a parent involved, even if that parent is angry, since there's only one thing worse than an angry parent, and that's a parent that gives up, doesn't care, and won't engage any more.