McGuffey Readers were a series of graded primers for grade levels 1-6. They were widely used as textbooks in American schools from the mid-19th century to the mid-20th century, and are still used today in some private schools and in homeschooling. The method pursued is the same as that in McGuffey's Revised Readers, and the greatest possible care has been taken to insure a gradation suited to the youngest children. Only about six new words are to be mastered in each lesson. These new words and the new elementary sounds are always to be found in the vocabulary of the lesson in which they are first used.