By Stephen M. Silverman And Simon Perry
Updated June 12, 2003 11:35 AM

Prince Harry whooped a celebratory “Yes!” and raised his fists in delectation as he stepped out of high school on his last day of classes Thursday morning, PEOPLE reports from its London bureau.

Harry, 18, who had just completed the last paper of his geography exam walked out of Eton College to set off on a long, hot summer of polo, parties and traveling — but not before bidding a fond goodbye to his housemaster Dr, Andrew Gailey, Gailey’s wife Shona and his dorm’s matron, Julia Thomas.

He then rode off in a police-escorted Land Rover Discovery for the two-hour drive to his father’s country home, Highgrove.

Earlier in the day, a casual-looking Harry (wearing an open-necked blue shirt, long, baggy khakis and a gray jacket) loaded up the last of his belongings and hauled out the rest of his clothes in a black, plastic bag.

“He had spent some time carefully folding everything and then just threw it in the bin liner,” a bemused royal source tells PEOPLE.

“In the next few weeks, he is going to relax. He might go away but we don’t know at the moment,” a palace source adds. “I am sure there will be a lot of polo.”

Later this summer, Harry — considered less academic than his brother William — will take the first steps on the way to a career in the army when he takes the pre-Regular Commissions Board assessment. This will test whether the third in line for the throne is suitable for a commission in the armed forces.

Sources at the palace do not know which regiment he hopes to enter.

Meanwhile, employees in Prince Charles’s office were left red-faced Thursday after they issued a press release to mark Harry’s departure from Eton, saying that when he took his place at the school he was accompanied by “his parents.”

In fact, Harry arrived at Eton in September 1998 — a year after his mother, Princess Diana, died in a car crash in Paris. Only Prince Charles was with Harry on that poignant day.

But then, palace officials used Thursday’s events to issue an official statement from Princes William and Harry urging that, while they were appreciative of the tributes and condolences they have received over the years, the mourning period for their mother should stop.

For a photographer’s look inside the life of Harry, pick up the latest issue of PEOPLE, on newsstands Friday.