My childhood might have been not wasted but my middle and high school years were definitely a waste.
I think the current primary role of schooling in society is to make teenagers busy and occupied and keep them under control, thereby
a) contributing to social stability
b) freeing up adults' time and effort, leaving more to focus on working.
From the teenagers perspective the current system is bad or markedly suboptimal because
a) Schools are poorly incentivized to instill market-relevant knowledge.
b)Teenagers form their own society within which criteria of social success and goals are highly distorted compared to productivity-oriented societies. For example, because there is a lack of "hard" status signals, (like the feat of establishing one's existence and wealth), status games based on factors that are irrelevant in later life are rampant and take up a lot of effort and and also cause great amounts of psychological damage to people who happen to be disinterested or uncapable of participating in the relevant status games (damage through bullying, isolation, etc.), even though some of these people will have superior productivity and affluence in adulthood (geeks, nerds being the archetypical example).
c) At the same time, because teenagers are really NOT integral parts of greater society, there will be an inevitable source of distress and social tension: our evolved psychology "expects" full social integration at teen ages and interprets being shoved away in schools as an attempt to keep them away from power and influence. Various forms of teen rebellion and drama ensues.
d) As I touched on, schooling makes transition to adult ways considerably harder and leave people ill equipped. Also, because people are naturally resistant to change of social order, several societies are formed that attempt to preserve school-like environments. The stereotypical partying college students are an example. Note that this imparts further social costs.
Apprenticeship's benefits:
a) it integrates young people early with greater society, instilling lifelong relevant value sets instead of temporarily relevant distorted values.
b) there is no cost of transition to adulthood and refinement of useless skills. Also, no need to unlearn actively harmful school habits (learning-as-guessing-the-teachers-password-to-good-grades instead of understanding being the archetypical example).
Apprenticeship's costs:
a) for adults it is very costly and time consuming to tutor and cultivate youngsters directly.
b) the general well-being of apprentices has much greater variance than the general well-being of school attendants. In school there are many teachers and the legal rules and operating standards are (in theory) consistent and universal among most schools. In apprenticeship fewer people exercise more power and influence over apprentices. This drawback, of course, could be ameliorated by appropriate legislation and regulation, but it would be somewhat more complicated and much harder to enforce than schooling regulation.
c) Apprenticeship leaves a lot less room for a state to instill specific values or to exert collective influence in any ways.
Question: why do we have schooling instead of apprenticeship?
A naturally occurring answer (which I believe to be largely correct) is that the benefits of apprenticeship are mostly to young people and the costs of it are mostly to adult people, and adult people has most of the influence and power in society. Obviously, the policies are either optimized according to policymakers' criteria or biased towards those criteria to some extent.
Now, I personally think that high school is most skewed towards adult interests and is the most detrimental to teenagers. However, elementary school and possibly middle school is probably still desirable, because there is a great benefit to society if basic literacy and math skills are universally attained. Of course, elementary and middle schools should be reformed so that they do not address the challenges and requirements of high school but instead apprenticeship.