WASHINGTON — Open your notebooks and sharpen your pencils. School for thousands of public school students is about to get quite a bit longer.

Five states were to announce Monday that they will add at least 300 hours of learning time to the calendar in some schools starting in 2013. Colorado, Connecticut, Massachusetts, New York and Tennessee will take part in the initiative, which is intended to boost student achievement and make U.S. schools more competitive on a global level.

The three-year pilot program will affect almost 20,000 students in 40 schools, with long-term hopes of expanding the program to include additional schools — especially those that serve low-income communities. Schools, working in concert with districts, parents and teachers, will decide whether to make the school day longer, add more days to the school year or both.

A mix of federal, state and district funds will cover the costs of expanded learning time, with the Ford Foundation and the National Center on Time & Learning also chipping in resources. In Massachusetts, the program builds on the state’s existing expanded-learning program.

Spending more time in the classroom, education officials said, will give students access to a more well-rounded curriculum that includes art and music, individualized help for students who fall behind and opportunities to reinforce critical math and science skills.

“Whether educators have more time to enrich instruction or students have more time to learn how to play an instrument and write computer code, adding meaningful in-school hours is a critical investment that better prepares children to be successful in the 21st century,” Education Secretary Arne Duncan said in a statement.