Talking Teaching

March 3, 2010

breadth vs depth

Filed under: science teaching — Tags: , , , — alison @ 9:49 pm

This is another re-post from the Bioblog. It was written to draw attention to an issue that I feel rather strongly about; that is, the conflict between teaching a few key concepts in depth, encouraging student understanding, and teaching a whole heap of material in the same period of time, which often sees students resorting to rote learning as a coping mechanism. I’d be interested to hear what you think of this one.

One of the conflicts faced by probably every classroom teacher is the one between the amount of material one has to teach (& the students to learn about) and the time available. I face it myself: huge (though also very good) textbook, requests from my colleagues to make sure that the first-year course adequately prepares students to take second-year papers, students coming in with a range of backgrounds & prior experiences of biology – & a 12-week semester in which to accommodate it all. Reflecting on my teaching practice over the last several years in our A semester intro bio paper, I think I probably teach less content, less detail, than when I started in this particular paper, but have more of a focus on identifying (& dealing in depth with) big, or key, ideas. As you’ve probably guessed from my posts, I encourage my students to think critically about what they’re learning, and to gain an understanding of how those ideas & concepts relate to each other. And of course I’d like all my students to view science as fascinating, fun, useful, & relevant to them in their daily lives…

So of course I was interested in a paper by Marc Schwartz & his colleagues, entitled Depth versus breadth: how content coverage in high school science courses relates to later success in college science coursework. How would their findings relate to my own teaching approach? (And, is what I do in the classroom supported by empirical data, or is it a case of intuition & experience leading me up the garden path?) In a survey of 8310 students taking first-year biology, chemistry, & physics courses, the authors fround that students who said they’d spent at least a month studying at least one major topic in depth, while at high school, received higher grades in their university science classes than students who hadn’t done (or didn’t remember!) doing any in-depth work. Interesting! The team also looked at the outcomes for students who reported having broad high school classes that covered something on all major topics. The results here were equally interesting – these students didn’t seem to have any advantage over students who hadn’t ‘studied everything’ in physics & chemistry, & were at ‘a significant disadvantage in biology’.

Presumably students spending a month or so on a single topic can really come to a good understanding of the area, mastering key concepts & able to understand how it all fits together. Taking a ‘deep learning’ approach, in other words.  In classrooms where there’s a drive to cover everything, it could well be that many students cope with the huge volume of material by using learning approaches that could be called ‘shallow’ – rote learning techniques, for example, that don’t really aid a thorough understanding. (All this, of course, assumes that the tertiary assessment practices these students are encountering reward those taking the ‘deep’ learning approach to their studies…) And those with the learning skills developed by taking a deep learning approach to one topic can then apply those to the new material they learn in the following year, enhancing their learning outccomes there as well.

I guess my fondness for trying to focus on teaching methods that encourage ‘deep’ learning reflects my own philosophy that there is simply too much information potentially available. In ‘the old days’ it was probably quite possible to teach a subject such as any one of the sciences in fairly comprehensive breadth. But since then, particularly with the advent of modern technology, there’s been something of an explosion of knowledge. I know some of my students are quite daunted by the sheer size (& volume of content) of our textbook (the excellent Campbell [no relation!} & Reece). For me, & my colleagues in first-year biology, the question is, how to include it all? And,  should we cover it all? Schwartz et al quote another author as saying that ‘[to] be successful [in their learning], students need carefully structured experiences, scaffolded support from teachers, and opportunities for sustained engagement with the same set of ideas over extended periods of time.” That ‘sustained engagement’ part is the tricky one, when you’re teaching a ‘service’ course that’s intended to prepare students for a range of paper options in their next year of study. I try to manage it by identifying common themes (eg the need for gas exchange, internal transport, energy) that apply across the living world, & tying things to those, so the themes recur even if the material attached to them is novel. But it’s a testing balancing act, nonetheless… Nice to know that at least one research paper suggests that I’m on the right track :-)

M.S.Schwartz, P.M.Sadler, G.Sonnert & R.H.Tai (2009) Depth versus breadth: how content coverage in high-school science courses relates to later success in college science coursework. Science Education 93: 798-826 doi 10.1002/sce.20328



  1. Nice post!

    I’m a physics teacher here in the Philippines, and I have been shifting a lot from bookish teaching to experiential teaching. I trust that my students can read the facts from the book. But the better “glue” to help these things stick is not repeating these things in class. Experience and application will be.

    I’m sharing this with my peers teaching biology.

    Comment by jvsalayo — June 26, 2010 @ 9:27 pm

  2. Thank you! Please let us know how you get on with your changes in the classroom. I am sure it will work out well for you & your students (although you may find some resistance from some of the students at first, if they are used to & expect the ‘book-learning’ approach.)

    Comment by alison — July 1, 2010 @ 10:47 am

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