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.