The phrase "a third school of" is correct and usable in written English.
It can be used when discussing different categories, theories, or approaches within a particular field or subject.
Example: "In the debate on educational methods, proponents of a third school of thought argue for a more holistic approach to learning."
Alternatives: "an additional category of" or "a separate branch of".
A third school of thought blames histamines.
A third school of thought points to investment in ideas and new technologies that outlast their inventors (the economist Paul Romer has made some major contributions here).
A government that owes its legitimacy entirely to growth will find it hard to contain the disappointment that a slowdown will entail.This special report subscribes to a third school of thought.
A third school of thought supposes that there may have been a problem with the mixture of patients selected for the study.The NHLBI will not publish the results of its investigation for another six to eight weeks, but Dr Nabel has told The Economist that her team has ruled out several of the speculations.
There's a third school of thought which says "Quit trying to force-feed her your idea of what she should be into and let her figure things out for herself, you fucking spaz" but that's for hippie guidance counselors and parents who let their kids wear basketball shorts to Unitarian church/temple.
A first school of thought, known as the primordialist approach, explains ethnicity as a fixed characteristic of individuals and communities.
In 1905 Young became principal of the Chicago Normal School (a second school of that name, later Chicago Teachers College, now Chicago State University).
According to a second school of thought, Malthus et al. weren't wrong, exactly; it's just that their timing was off.
The draft proposal takes many of these concerns into account, but it also reflects the concerns of a second school of thought, one that cautions against hasty and simplistic solutions and asks important questions.
