Activities and projects have their place when used to enhance understanding of academic subject matter. In other words, they should be a means to an end, not an end in themselves. More often than not, they have become an end in themselves.
Here are some of the reasons for this mania (from Illinoisloop.org):
WHY So Many Projects?
Why is this happening? Why have schools been turned from places of learning into places of low-challenge activities? The blame can be fixed with several converging theories that together have overwhelmed schools and teachers:
Constructivism: The pervasive education religion of "constructivism" holds that a child learns best through active "doing". To some extent, this is of course true. However, the Achilles heel of constructivism is that this is a painfully plodding and tedious way of learning, while forcing a drastic reduction (dumbing down) of the content of a course. While an active project may often be a good technique for making a difficult concept clear, it is often used when a simple direct method would be just as effective and far more efficient.
Groups: The pressure for "collaborative learning" or "cooperative learning" is usually implemented as nothing other than projects and activities.
Interdisciplinary curriculum: Teachers are under pressure to find "thematic" or "interdisciplinary" links between subjects. There is nothing inherently wrong with that -- the Core Knowledge Sequence used in the Core Knowledge schools is carefully constructed to encourage learning in this way. But without a rigorous, well-reasoned curriculum like the CK Sequence, the result too often is time-wasting art or writing projects linking vague language arts goals with minimal content points.
Multiple Intelligences: The fevered success of another fad, Howard Gardner's Multiple Intelligences (click for much more info on that), pressures teachers into coming up with separate projects for each of this theory's supposed categories. So, we have one project to appeal to "kinesthetic" children, another project for the "intrapersonal" learners, we sing a song for the "musical" learners, and so on. Of course, since the MI mindset offers no method to identify or quantify these supposed differences, the bottom line is lots and lots of projects for all the children in the class.
Anti-Fact Mentality: Starting in ed school and throughout their careers in most schools, teachers are subjected to a barrage of rhetoric about the dangers of teaching facts. They are told not to teach "mere facts" to be "regurgitated." Learning of specific content knowledge is called "low level" and nothing more than "memorization." What used to be called "learning" is now disparaged as "brain-stuffing". A teacher is to be "a guide on the side" rather than "a sage on the stage." This drumbeat from the ed schools and education orthodoxy is pervasive and relentless, and teachers are drilled incessantly (ironic, isn't it?) that direct teaching is to be avoided. So, if the teacher isn't teaching, what are the kids likely to be doing? Yup, more projects.
Anti-Fact Assessments: If facts are bad, then testing whether children know facts is even worse -- or so teachers are told. Thus, chapter tests and other quantitative measures of learning are deemphasized in favor of so-called "authentic" assessment, in which we look at a whole "portfolio" of a child's "work" which largely consists of (ta da!) projects.
"Authentic" Skills: If the purpose of a school is not to build knowledge, then what is a school for? The progressivists have a ready answer for that: to learn supposed "skills." They argue that since knowledge is always increasing, it is hopeless to try to teach very much at all (using a twisted logic that defies comprehension). What kids need, they say, is to learn how to look things up. Well, guess what? Projects give them an "opportunity" to look things up instead of being taught.
Innovation: School administrators suppose themselves to be seen as "creative" or "innovative." We often read of a school calling itself "innovative" or a teacher said to be "creative" ort "imaginative." Those are fine attributes, but not when they take the place of words like "effective" or "knowledgeable." One teacher might be extraordinarily effective and captivating in teaching children a rich, detailed and memorable introduction to American history, while another teacher gains more recognition from parents and maybe the local newspaper not by teaching much of anything but by staging a marathon dress-up pageant, puppet show or enormous craft project.
Finding a Use for Computers: Projects provide a convenient raison d'etre for the expensive computers that schools have been buying in bulk.