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Cause and effect can be remote in time and place in a system. Consider an airline system. Around Easter in 2000 an error by a service truck driver in Sydney caused damage to the rear door of a plane . This resulted in several people being more than a day late getting home from the Gold Coast (Queensland, Australia) to Tasmania (Australia's island state to the south of the mainland). The Gold Coast and Tasmania are several hundreds of kilometres from Sydney. Who knows the impact on individual lives (appointments missed, opportunities lost ...) arising from the service truck driver's error.
Then there is the story of the person who was reprimanded by the boss. On arriving home, still upset, the same person snapped at their partner who promptly growled at their child to 'Get on which your chores!!!!". The child went outside and kicked the dog. And the dog didn't even know of the boss' existence.
Schools are very subject to such 'unknown' cause and effect relationships.
The Hawthorn Effect is very real. Studying an aspect of the school, or an individual's performance, will impact on how the people concerned behave. Involving a person directly in the study of their own purposes, actions and achievements has an even greater impact.
Quality is based on learning about the system. Everyone in the system can contribute significantly to that learning. The tools and methods provided by quality enable us to both understand, study and improve the systems in which we operate.
The lesser alternative is that, without a good understanding of the system and its processes, we tend to turn to external experts to 'tell us what to do'.