April 17, 1965 was the largest anti-war protest to have been held in Washington, D.C. up to that time.
The number of marchers (15,000–25,000) was close to the number of U.S. soldiers in Vietnam at the time (less than 25,000).
Teaching the Vietnam War: Beyond the Headlines is a collection of lessons for teaching about the Vietnam War and the antiwar movement.
Also see an exam prepared by Students for a Democratic Society (SDS) on the war. In the introduction to the document is the explanation,
Instructions: This examination has been prepared to allow you to check your understanding of the war in Vietnam. We believe in the importance in a democracy of putting facts in the hands of every citizen to enable him to participate in decision-making. This is particularly true where the question is war and peace, and where the citizens are the young men who are called upon to fight.