We will soon be launching an education site that teaches people how to drive (not really the topic, but it will do). We plan on being content rich and have plans to expand into several "schools" of driving. Currently, content falls into a number of categories, for example rules of the road, shifting gears, safety, etc. We are going to group content into general categories that apply broadly, and then into "schools" where the content is meant to be consumed in a specific order.
So, for example, some URLs in general categories may be:
Then, schools will be available for specific types of vehicles. For example,
We will provide lessons at the school level, and in the general categories. This is where it gets tricky. If people are looking for general content, then we want them to find pages in the general categories (for example, drivingschool.com/rules-of-the-road/traffic-signs). However, we have very similar content within each of the schools (for example, drivingschool.com/motorbikes/rules-of-the-road/traffic-signs).
As you could imagine, sometimes the content is very unique between the various schools and the general category (such as in shifting), but often it is very similar or even nearly duplicate (as in the example above). The problem is that in the schools we want to say at the end of the lesson, "after this lesson, take the next lesson about speed limits for motorcycles" so there is a very logical click-path through the school. Unfortunately this creates potential duplicate content issues.
The best solution I've come up with is to include a canonical tag (pointing to the general version of the page) whenever there is content that is virtually identical. There will be cases though where we adjust the content "down the road" 
to be more unique and more specific for the school. At that time we'd want to remove the canonical tag.
So two questions:
- Does anyone have any better ideas of how to handle this duplicate content?
- If we implement canonical tags now, and in 6 months update content to be more school-specific, will "undoing" the canonical tag (and even adding a self-referential tag) work for SEO?
I really hope someone has some insight into this!
Many thanks (in advance).
