According to the U.S. Customs and Immigration Services, those hopeful of becoming U.S. citizens must "be able to read, write, and speak basic English." They must also "have a basic understanding of U.S. history and government (civics)."
While the immigrants apparently pass the minimum test, CIS looked also to a more authoritative test conducted by the Program for the International Assessment of Adult Competencies and found that in reality
many immigrants are functionally illiterate. The tests, done before President Trump took office, suggest that 32 percent of all naturalized citizens speak English "not well or not at all." Of those,
nearly half were Hispanics.
https://www.uscis.gov/citizenship/teachers/naturalization-information