Final answer:
The laws mandating English as the language of instruction for public schools in the first half of the twentieth century were largely in response to immigration concerns, standardized intelligence tests, and the idea of the cultural melting pot.
Step-by-step explanation:
The laws mandating English as the language of instruction for public schools in the first half of the twentieth century were largely in response to the trend of massive immigration around 1900 and concerns about the loss of a common language and control of society to foreigners. These laws were also influenced by the development of standardized intelligence tests in the 1920s, which were only available in English, and parents and educators wanted to ensure that students performed well on these tests. Additionally, there was a belief among some foreign language speaking immigrants that their children should speak exclusively in English as part of the cultural melting pot of the United States.