I don't have at my fingertips the exact figure for the percentage of online versus print material in terms of the uses in classrooms, but I would suggest that teachers are subject to their own personal purchasing power—that of the school. For example, teachers don't purchase textbooks on an individual basis. They would be purchasing individual materials to use for either developing a curriculum or building a unit for their students. Depending on the complexity of the classroom, they may require different types of access to material. The concern that teachers are looking at right now is what they are subject to in terms of the use of material that is purchased and that they've already brought into their classroom to augment the curriculum development.
What we're talking about right now through fair dealing is that it allows excerpts to be used by teachers. On the notion, for example, that whole textbooks are being printed, I can say for a fact that in terms of the budgets in a school or a teacher's individual purchasing power to be able to photocopy, that's unheard of. In fact, many teachers across the country are subject to specific accounts that limit the amount of photocopying they're allowed to do. Necessarily, when you're talking about your own developed material and the materials you would be using in your classroom, going out and printing something that has copyright applied to it is wasteful, and it's not used in that sense.
As digital material is brought into the classroom, it's cited so that students are aware of it when they are using it in their own research. Teachers do talk to students about the development of copyright citing and about giving credit for material and thoughts that are not their own. That's generally the use in K-to-12 classrooms.