The White House reopened to public tours on Tuesday for the first time since the inauguration, and President Trump celebrated by popping out from behind a wooden screen to surprise a group of schoolchildren.

The children erupted in cheers and screams of delight as Mr. Trump emerged from behind the screen with his mouth and arms wide open. He personally greeted a fifth grader from Birmingham, Ala.

Thousands of people visit the White House each year. The tours were on a seven-week hiatus, allowing the new president and his staff to settle in.

In an odd turn of events, Mr. Trumps’s surprise took place in what appeared to be the White House’s ground floor, where tours typically start, in front of a portrait of his opponent in the election, Hillary Clinton, dressed in a black pantsuit and smiling radiantly as first lady in the 1990s. It was not clear if that was intentional. Pool reporters were present at the time, but were told they could not ask President Trump any questions.