It is hard not to agree with some of what is written in Reforming Education, a collection of essays by Moritmer Adler, describing his vision of what schooling and education should be. Unfortunately, as an actual educator, it is easy to agree with much, also.
The overall theme of this collection is Adler's belief that a liberal arts education, which teaches a student to "read, write, and think well," is the best education for a democratic - by which Adler means egalitarian - society. Adler, like Dewey, draws a strong link between democracy and education but, unlike Dewey, suggests that specialization - offering different "tracks" to suit different students - is undemocratic. Adler suggests that all students should be educated with the same curriculum and, in an often repeated quote, suggests that "the best education for the best is the best education for all."
Unfortunately, Adler doesn't defend this idea very well and relies more on rhetoric than argument. He addresses the very practical suggestion that students of differing abilities and proclivities might be ill-served by recieving the exact same education (and, as an educator, I can certainly attest that different students are capable of diffeernt things), but he very casually dismisses this criticism as undemocratic and pessimistic. (He also relies on an analogy of two different sized containers that need to be filled with different amounts of the same liquid, which shows that Adler has never taught students with drastically differing abilities, for if he had, he would realize that subjects like Algebra II may not actually be accessible to all students.)
Alder rightly takes to task those who want drastic differentiation and specialization in k-12 but, I think, errs in the opposite direction by ignoring the importance of electives and occupational training (especially for those who plan not to stay on an academic track after 12th grade). The aboliton of electives means that we ignore the importance of students' being able to, in some degree, study things that interest them. (Adler, I think, does not see that we can allow students to sometimes study what interests them without letting them do so all the time. In this, he is just as extreme as Montessori in the opposite direciton.)
To Adler's credit, he repeatedly insists that schooling should first and foremost teach a student how to think, and that k-12 should be called schooling rather than education (which is the lifelong process of using the tools from schooling to expand one's thinking.)
But in the end, I think one of Adler's biggest mistake - typical of philosophers who's only knkowledge of what pre-college school is like is found only in their imaginations and reading of other inexperienced philosophers - is that he has no clue of what kids are actually like. He makes the "philosopher's mistake" of assuming that the sample of students he meets in his college courses must be a good represenation of what all kids are like. Students, therefore, probably all really like philosophic subjects, will all probably reach "happiness" by reading great books in their leisure time, and will certainly need to know the wisdoms contained in the arts and letters in later life.
While this is certainly an interesting idea, it leads Adler astray in many areas. His disdain for vocational education - training students to be "wage slaves" or just "slaves" - is just as ignorant as excessive vocational tracking, as it underprepares students who will not go on to intellectual vocations (though it will well prepare our future lawyers). Adler correctly acknowledges that teaching students to think is itself good preperation for life, but ignores the fact that, for many, so is learning practical skills. His suggestion of moving vocational training to the college level would have the devestating consequence of forcing students who cannot afford college (often the students going into blue collar vocations) to graduate high-school wholly lacking in training for a job.
I do agree - as I think most proponents of differentiation in high school - that the primary goal of schooling is to train students how to think and to discipline the mind. I could not help but read Adler's suggestions, though, as extremizing a good thing. 'No electives, no career training, only liberal arts,' may sound nice but would, I fear, result in a "one size fits all" system that is unjust because it is inflexible and inatentive to difference in students' needs and abilities.
As with so much else, the wisdom is in balance between two extremes, not replacing one extreme with another. For those interested in Adler's ideas, a less extreme approach to essentialism in education can be found in the works of William Bagley and Leon Kandel.