Final answer:
The ideas and information in section 2 of Gladewell's text provide background and historical context that support his discussion of summer vacation in section 3.
Step-by-step explanation:
The ideas and information in section 2 of Gladewell's text on the history of the U.S. public school system (lines 53-115) support his discussion in section 3 about summer vacation (lines 116-221) by providing background and historical context. In section 2, he examines the development of the public school system, including the expansion of public school enrollment and the growth of high schools. This information helps set the stage for his discussion in section 3 about summer vacation's role in the context of the overall school system.