RE: Difference between PBL & TBL
Currently I am teaching social studies 11 & 8 on my BEd practicum, where I had hoped to implement TBL at the secondary level. Immediately I found the prospect much more difficult than one-class applied skill PBL scenarios which can build on previous knowledge & skills. There are several reasons why PBL appears more appropriate in this particular class set than TBL which I'll share with you.
One large barrier I faced that is different from post-secondary is that secondary schools appear to be largely against the flipped classroom and assigning homework is increasingly being frowned upon as taking up 'leisure time' or even promoting plagiarism, when work can be assuredly original when supervised in-class (especially for writing).
Another barrier I faced is the low functionality or intrinsic motivation of high school students. I usually only think about going as far as the RAT stage for the SS11 provincial exam content. They lack the focus and self-discipline to work in groups and stay on task as easily as university students. SS8 may lend itself better, though I don't see much more motivation happening, with 4 more years of highschool to look forward to.
Some teachers are against keeping students in one permanent or semi permanent group, preferring to expose younger students to a greater variety of work conditions, attitudes, and people. This was the primary reason a TBL unit was rejected by my supervisor.
Although I haven't tried it, I have some doubts as to the feasibility of the peer-review accountability system in TBL in high school. Hard feelings might arise if the identity of reviews becomes known, especially in jr. grades for students who will continue to be in the same cohort for years. I have heard teachers support the idea of personal reflection but feel uncomfortable with peer review of already sensitive teenagers.