In the era of digitization, education has evolved to meet the demands of the modern age. An increasing number of students are now opting for online high schools. A recent industry report has shed light on this burgeoning trend, offering substantial insights into the top online high schools, and the key findings are indeed fascinating.

Starting with an analysis of the 'why' and the 'where,' the increased predilection for online high schools is rooted in the convenience they offer. They provide access to quality education irrespective of geographic boundaries, implying a significant democratization of learning opportunities. The availability of advanced resources, such as virtual labs, multimedia lessons, and interactive simulations, all contribute to the appeal of these institutions.

The report, rich in quantitative analysis, identifies some key players in the online high school sphere. Schools such as Stanford University’s Online High School, University of Nebraska High School, and George Washington University Online High School have risen to prominence. The success metrics of these schools are multifaceted; they include student performance, graduation rates, college placement success, and learner engagement.

Let's delve into the numbers that underpin these determinants of success. Stanford University’s Online High School boasts a staggering 100% college placement rate, while University of Nebraska High School's graduation rate hovers around 91%. George Washington University Online High School reports an impressive 95% student retention rate.

There is, of course, a theoretical underpinning to this success: these schools leverage extensive frameworks of cognitive psychology and pedagogical theory. For instance, Stanford’s program employs Hebbian Learning and Connectivism principles, where learning is seen as a process of creating connections and developing networks. This approach enhances the depth of knowledge and promotes critical thinking, explaining the college placement success of their students.

On the other hand, George Washington University Online High School has adopted a more individualized approach, operating on the principles of Vygotsky's Zone of Proximal Development, offering personalized guidance based on the individual learning capabilities of a student. This approach is reflected in their high retention rates.

Analyzing further, the report highlights several intriguing trends in the online high school landscape. The discourse on the 'when' and 'how' reveals a significant surge in enrolment during the last academic year, likely a direct result of the global pandemic causing traditional schools to shutter. Furthermore, the 'how' is being innovatively addressed by these schools via technology. With the advent of AR and VR, learning has been transformed into an immersive experience, which has been found to improve comprehension and retention significantly.

However, it would be remiss not to mention the potential tradeoffs of online high schools. While they offer considerable advantages, there are potential downsides. The lack of immediate face-to-face interaction could potentially impede the development of necessary social skills. Furthermore, self-discipline and motivation are crucial for success in an online environment, which can be a challenge for some students.

In conclusion, the rise of online high schools signals a significant shift in our educational landscape. They are not merely a temporary solution during a pandemic, but a legitimate, perhaps superior, alternative to traditional high schools. This paradigm shift is not without its complexities and challenges. As we continue to explore this brave new world of education, it is essential to consider not just the quantitative metrics of success but also the qualitative aspects of the learning experience. However, as the report suggests, with their focus on individualized learning, innovative teaching methods, and advanced technology, the top online high schools are already paving the way for the future of education.