And is the rarest of constitutional consequences, impeachment by the House and then possible conviction and removal from office by the Senate, worth the trouble a year before the next election — the first in which the students in Mr. Dier’s class, most of whom are 17 years old, will be eligible to vote?

Chalmette High is in St. Bernard Parish just southeast of New Orleans, along the Mississippi River. Surrounded by water and built largely upon fishing and oil refineries, the parish lost more than half of its population after Hurricane Katrina destroyed nearly every home. The rebuilding brought more diversity, and today, of the 1,972 students at Chalmette High, about 52 percent are students of color.

Mr. Trump handily carried the parish in 2016 with about 65 percent of the vote, but the students in Mr. Dier’s class did not always share their parents’ conservative views.

Mr. Dier, 31, teaches in the same classroom where his mother, also a world history teacher, taught five years before. He had planned to tackle impeachment later in the semester, but when the Democrats began an inquiry last month, he moved those lessons up on the calendar to follow a study of the Vietnam War.

He said the point was not just to study this particular impeachment inquiry, but to push his students to engage as informed citizens at a time when many Americans do not understand basic civics.

Only 39 percent of adults can name all three branches of government (a jump from 32 percent last year) and 25 percent can name only one branch, according to a recent survey by the Annenberg Public Policy Center at the University of Pennsylvania. This year, congressmen in Florida and Georgia introduced a $30 million bipartisan bill to improve the quality of civics education in elementary, middle and high schools across the country.