There are several “schools of thought” in software testing. People who rigidly adhere to one school are very idealistic about a theory of software testing. Older and wiser testers mix and match schools, styles, systems, theories, practices, to fit each new given situation.
With Software Test & QA matured as an industry of its own, there is a well established “non-school school of thought” that embraces the mix and match approach, according to the context of each new project. It is usually called the “Context-Driven Approach” to software testing.
If you’re reading this, you’ve probably heard of it. But you may still think it is a school of thought. Instead, think of it as “how a smart tester with vast knowledge and expertise, who knows all the schools and has experienced dozens of project situations, might pull together the best ways to handle a new project in new circumstances.” In software testing, let your experience serve you well—let everything you’ve learned guide you through each new context.