Teachers—especially those of English or the arts—rely on famous works of literature, music, and film in their classes, copying and repurposing them to analyze with students.

But often, embedding these works in curricula to share with other teachers or making them available to students can raise questions about copyright: How much of an original movie or poem can a teacher include, and how widely can resources made with these materials be distributed?

As of Jan. 1, thousands of works are newly exempt from these questions. At the beginning of 2019, anything that was originally copyrighted in 1923 passed into the public domain—meaning that anyone can use and reprint it, free of charge and without permission.

Teachers can now post the full text of Robert Frost's poem "Stopping by Woods on a Snowy Evening" online for students to access, or organize a community screening of Cecil B. DeMille's classic film The Ten Commandments—both originally published in 1923—without having to worry that they might be in violation of copyright law. Books by Edith Wharton, P.G. Wodehouse, e.e. cummings, and Virginia Woolf have also cleared the end of their copyright terms, as have two violin sonatas by Bela Bartok.

Why has it taken almost 100 years for these copyrights to expire? In 1999, Congress passed the Copyright Term Extension Act, which extended protections for rights holders for 20 years. That created a two-decade gap between the works of 1922—which passed into the public domain in 1998, before the law was passed—and those of 1923.

In the meantime, the rise of online lesson sharing sites has raised thorny copyright issues for teachers. As I wrote recently, some teachers on the lesson marketplace Teachers Pay Teachers are profiting from materials adapted or taken wholesale from other educators. Many teachers may not realize that repurposing another educator's work for sale on that site could violate the creator's rights, or that they're generally infringing copyright by pulling a photo or image from the internet that they don't have permission to use.

Of course, even before books, movies, and musical compositions passed into the public domain, teachers looking to reprint and distribute them in part could have claimed fair use—an exception to copyright law that allows excerpts of protected material to be used for criticism, research, journalism, or teaching without permission or payment. But what counts as fair use is decided in court, and educators could still have faced legal challenges—especially if they distributed or sold their work to other teachers.

See also: Copyright Confusion Is Shortchanging Our Students (Opinion)

And having these works in the public domain doesn't just permit sharing—it also enables access. These materials can now be digitized and archived online for free, so teachers and schools won't necessarily need to buy them in order to use them in class.

Looking for these books, poems, and movies to use in your classroom? Duke University's Center for the Study of the Public Domain has listed (and linked to copies of) some of the most well-known titles. And the digital library HathiTrust has compiled over 50,000 works that are now freely available.

Photo: Poet Robert Frost shown in 1924. —AP