There is a middle ground between a strict TAB (Teaching Artistic Behavior) and the Traditional Project Approach, it's where I live. I do projects with specific media and over-arching themes, but incorporate student choice in how they express and personalize their work in such a way that no two projects will be the same. For example: Gargoyles with plaster that protect you from a personal fear. Every fear is different, symbols to combat that fear will differ as well. Even if 2 kids have a fear of spiders they will express it differently, uniquely, personally, and I will still have one major demo instead of twenty individual ones.

In going with a theme of fear without a connection to a movement, history, or historical theme--in my example, gargoyles--would be expressive, but less connected to core content, something that is very important to me for reasons I have stated in other posts. HERE, HERE, and HERE.

I am assuming we don't just tell them "make something that shows me your fear with any material you like..." but that we instruct students about the history of fear-based/nightmarish artwork--The Scream, Guernica, etc.  The element of choice is key, and is that "middle ground," between tight control that can lead to cookie-cutter-art, and an "open studio" on the other end that may lack the kind of structure and core connections I feel are important.

Most art teachers are somewhere in the middle though they may be more comfortable on one side of the spectrum or the other. There are as many different approaches being used as there are art teachers, and all are valid for their students, situation, budget constraints, and comfort level.

I believe that "choice" in the portion of the lesson that connects with the child is the key element. I think the importance of choice of media is a "false" one to argue. I can express fear through painting, sculpture, clay, paper cuts, etc and it will not hinder the expression or results. My decision as the teacher, to focus on a particular media is grounded in budget, availability, the particular students I have, and knowing what I want them to have mastered within their year with me.

I believe that students need to learn to use a broad range of media with depth. If I let them "have at it" with anything, either they will not use the media fully, or focus on only the few they are comfortable with and not challenge themselves, or I will be so spread thin helping all I cannot help them individually, nor will I know at the end of the year what each child will have been exposed to.

I have found that teaching through a specific media is important for mastery and frankly produces "good results." Though we may not like to admit it, the "results" you display do say something about your program... BUT judgement on that alone would be hollow.

So I set an overall theme. "Fear" in my example, as it's universal. Though sometimes I have students make a list of topics and choose one to follow. They get more "choice" as the year progresses, often the last project being whatever media they have used thus far. Sometimes I tighten the theme and loosen the media or vise versa.

That said, I find many students are overwhelmed by choice, and they either fall behind, create projects lacking depth, or waste space, media, and time.

I include "choice" because it's key to the personal expression and outward appearance. Media and mode choice is not "as" important in my experience, and choosing only the color of a crayon to make a project, if the only choice, is not choice at all.

For a living example, look at this LINK.

If you only consider the painted works (media), they are all inclusive of a theme (Christmas Tree), yet all are unique and expressive. What makes them different is the artist's CHOICE of expression; in this sample, an artist from history.

"Choice" is a nice term to throw around but WHERE that choice takes place is the important part.

After seeing a video about Dave DeVries, founder of The Monster Engine, I was inspired to have my high school students collaborate with lower elementary students.  I connected with fellow art teacher Judy Maida who had her students do monster drawings for Halloween. They were to be black and white line drawings on 8 x 10 inch paper, or about that size for ease of shipping. Her students did their initial drawings in pencil, and then traced them in sharpie.

When I received them, I had every work photocopied so we would retain an image of what the original looked like. These were paired for students as a reference to be photographed with their finished work. Before working though, my students completed several exercises to explore the basics of color theory, tonal value, gradations of color, and color transitions. They learned to make monochromatic color transitions as well as analogous and complimentary ones. They experimented with shading effects on drawn spheres and forms. When those exercises were complete and graded, they were allowed to choose a work from the monster pile.

Organization was an issue, so every student had a folder to keep ALL their work in. These were passed out and collected daily. I had several visuals up for students to see the process. Once they had an image they had to clean it up: erase the pencil lines, and finish any sharpie the child may have left incomplete. Sometimes it was a guess. We used no sharpie after that so that the original work would stand out with its original sharpie lines. Students worked right on the original, keeping the photocopy as a reference.

In hindsight, it would have been nice for the little kids to note on the back of their work their favorite colors and say if they wanted a scary or cute monster ala the "Monster's Inc." movies.

Knowing these would be holiday gifts, my high school students, many "rusher's," slowed down. I may have laid on a little guilt when some got lazy... "I hope that kindergartner won't feel sad if her drawing is the only one that didn't get done..." or high praise about how the kids will surely "treasure your gift." I shared stories of how I was influenced by my uncle's drawings, and wanted to be like him when I was a small child. It seemed to resonate for them, and they did really try their best. Only one student added some insensitive gore that I turned into "tar" with a black pen later.

They were graded on evidence of all the coloring techniques I had discussed with them. Their rubric was a check list; either the evidence was there or not.  I wanted to see all of the following: everything colored, monochromatic transitions, analogous transitions, complimentary color use in shadows, use of texture, backgrounds, smooth coloring with small pencil strokes. I think you can see, the results were quite spectacular. 

Posters Available Here.
Similar idea in 3-D HERE.

2018 Update: Here a father and son collaborate on a project together. This would be fun to do with a lower level class and an AP art class.

HERE is an interesting article from "Education Next" about the steep decline of school trips to museums in the last decade, and the measurable value they provide students.

"For example, the Field Museum in Chicago at one time welcomed more than 300,000 students every year. Recently the number is below 200,000. Between 2002 and 2007, Cincinnati arts organizations saw a 30 percent decrease in student attendance. A survey by the American Association of School Administrators found that more than half of schools eliminated planned field trips in 2010–11."

The article points out improvements in student recall, critical thinking, historical empathy, tolerance, and interest in museums.

Surprisingly, "One consistent pattern in our results is that the benefits of a school tour are generally much larger for students from less-advantaged backgrounds. Students from rural areas and high-poverty schools, as well as minority students, typically show gains that are two to three times larger than those of the total sample. Disadvantaged students assigned by lottery to receive a school tour of an art museum make exceptionally large gains in critical thinking, historical empathy, tolerance, and becoming art consumers."

If your own district had curtailed these trips, you may find that this new research is helpful in making your case.