Congress penned the fair use exception with educational environments in mind.  We'll talk more about that (below).  Legislators saw fit to extend further protections that exclusively apply to classroom environments.  The US Code contains specific exceptions for educators to use performances and displays of copyrighted work in section 110 of the Copyright Act. Understandably, busy teachers don't like being put in the position of interpreting broad or complex legal principles.  While I can't make these determinations for you, I'm happy to talk more about your specific needs.

In section 107, Congress notes that "multiple copies for classroom use" do fall under fair use.  But educators still wonder how much of a work they can copy, and under what circumstances.  Circular 21 from the US Copyright Office offers specific classroom copying guidelines.  These focus on brevity, spontaneity, and cumulative effect  (pp. 6-7). The circular recommends specific word limits for different formats  Teachers are instructed to ask for permission if time permits. They're directed not to copy more than one work from one author each term, or use the same work from term to term.  Keep in mind this document is a conservative interpretation of fair use that publishers have agreed to. Fair use may allow you to use more.

Case law is complicated on this question. Several fair use cases dealt with coursepacks produced by commercial copy shops, which doesn't shed much light on educators creating their own coursepacks. In a recent high-profile case, publishers sued Georgia State University for a fair use policy that allegedly encouraged faculty to infringe copyright.  While the results were mixed, the court found that only 5 of the 99 excerpts brought forward violated copyright.  Interestingly, the Eleventh Circuit Court, the last to speak on the case, rejected formulaic approaches to fair use, like those found in Circular 21, instead promoting case-by-case analysis.

Best Practices

• Don't copy a substantial amount from any one work. Use a small fraction: one chapter from a book, one poem, one article from a journal, or one image or graph from any particular work. You should be able to explain how each chapter or article relates to course outcomes or objectives.
• Don't share articles received via Interlibrary Loan (ILL) to Canvas. Circular 21 of the US Copyright Office discourages instructors from sharing ILL articles with every student in a class. This includes sharing such an article with students via Canvas. For articles that are not open access or to which the library does not subscribe, each student should request the article via Interlibrary Loan or Article Delivery. 
• Provide a citation for the work and a copyright notice.
• Link rather than copy when this is an option in digital environments such as Canvas.  
• Use library resources.  If the Libraries have subscription access to a particular article, a librarian can show you how to embed a stable link in your online course or syllabus.  You can also put books on reserve at the Valley Library.  You could also check if there's an e-book available, or request that the LIbraries purchase an ebook. 
• Don't copy consumables such as tests, workbook sheets, etc.
• When in doubt, get permission. If you need to copy a substantial amount of a copyrighted work, or if your use is in any other way impermissible, contact Printing & Mailing or Ecampus (if your course is online) about getting copyright clearance.