The U.S. Congress passes legislation establishing objectives and mandates, funding, etc. Each piece of newly-enacted legislation may affect the laws already in place by adding new language, amending existing language, reordering language, or deleting language. The process by which legislation happens has many steps, and publications are produced at various steps. The publications can provide useful insight into the objectives and challenges for a program you are researching.
Explanations of the legislative process and the publications produced at different steps are available from the Congress (see links from https://www.senate.gov/reference/Index/Legislation.htm, but my favorite source is "How a Bill Becomes a Law" from ProQuest. Click on any step in the process for an explanation.
Details about federal legislation: How might you find enabling legislation for a program?
Use the ProQuest Congressional database to find Congressional publications such as hearings. Search tips are at the right on the search page.
How far back the database goes with fulltext varies (see http://libguides.uww.edu/aecontent.php?pid=102774&sid=2287592). Testimony at Congressional committee hearings, for example, should be almost comprehensive since 1994, and less comprehensive 1988-1993. Transcripts of discussion at hearings is selective. If the full text is not available within the database, copy and paste the document title into the library catalog to see if it is available in Andersen Library's Federal Documents collection. Older materials (especially pre 1976) may not be cataloged, so write down the SuDoc number and ask for assistance with finding it at the Reference Desk. If Andersen Library does not have a federal document, we may be able to find it online or request it from another UW library.
For example, if you search for "school lunch" you will get results including Congressional documents, hearings, prints, reports, and more. It'll look something like this:
Click on a document type to go to that part of the results list, e.g., click hearings and then click on titles that sound promising. After clicking on a title you'll see descriptive information (hearing title, date, SUDOC number, pages, list of the witnesses at the hearing, summary, etc.) and in most cases links to the full text:
Click on a title and then on "Details" to see additional information including subject headings, which can be clicked to find more items on those same subjects or the words can be incorporated into your searches: