I hope most 17-year-olds don't need babysitters. We can probably split the difference some on this between elementary school (where the babysitting really is kind of economically important) and the older kids.
At that age you're fully capable of staying home by yourself and following online instruction, at minimum.
From a national perspective of producing competitive individuals in an increasingly international landscape? Yes, they do. They need at least a few hours of their day coached by an institution to direct their energies towards their studies.
Otherwise Khan Academy would already solve 85% of the problems, because it is closely aligned to state curricula.
Note that the median teenager (or lower), while possibly college-bound, is not really qualified for college and is not very academically inclined. Also note that they are decidedly not middle class or higher. They are constantly pushing and testing boundaries without the received wisdom to know when they have gone too far.
One of my biggest criticisms of modern day K-12 education, especially high school, is that it is mostly glorified baby sitting given the low amount of learning that takes place at the lower-end schools. The high school curriculum that we use today is roughly based on the same curriculum from late 1800s to early 1900s when only about 6% of people graduated from high school, and pretty much all of them went to college or a two-year school of some sort. High school was specifically designed to cater to college bound students.
A variant of this curriculum is used today even though approximately half of college-age students don’t go to college (including most high school dropouts). The curricular mismatch is a joke, and the only real reason high school can be justified for these students is, unfortunately, tax-funded babysitting.