Mika Stojsavljevic is due back at the Loughborough Amherst School in the United Kingdom on Tuesday.

But boy, does she have a great 'What I did over the weekend' story to share with the class.

Still a few months shy of her 16th birthday, the 6-foot Brit completed a wholly unlikely week here at the US Open Junior Championships on Saturday.

Showing poise and patience and demonstrating a fearsome serve, Stojsavljevic became the youngest US Open girls champion in 18 years, beating No. 7 seed Wakana Sonobe 6-4, 6-4 at the Billie Jean King National Tennis Center.

Stojsavljevic (pronounced STOY-Sav-Lee-ovich) is the first British girls' singles champion in New York since Heather Watson in 2009, and left no doubt her future is as bright as the lights at Times Square here.

“I think I'm still in a little bit of shock,” she said in her press conference about 90 minutes after her win. “I haven’t had time to process it yet.”

Asked how she thinks her classmates will treat her now, she laughed and said “yeah around school it might be a little bit different.”

Stojsavljevic, the youngest US Open girls' champion since Anastasia Pavlyuchenkova, also 15 years old, won in 2006, only had to play two three-set matches this week, and rarely looked rattled.

Case in point: After an early break of serve in the second set on Saturday, she held her own serve easily, facing only two break points.

And then, in the biggest game of her young life, serving for the match at 5-4 Stojsavljevic showed absolutely zero nerves.

She made all four first serves in the game, drilled two backhand winners, then won the match when a Sonobe backhand flew out.

Stojsavljevic collapsed in a heap of joy before rushing over to hug LTA coach Katie O’Brien (her main coach at home is David Brewer).

“The level was getting better and better as the match went along, and what a big occasion for her to stay calm,” O’Brien said. “I can’t tell you how proud I am of her. She got better each match, her confidence has grown each day.

“I don’t really know what to say, I’m speechless.”

Stojsavljevic was in the Wimbledon doubles final with partner Mingge Xu two months ago, but had the pressure all to herself in the singles championship match.

Sonobe had lost to Stojsavljevic twice previously in Grand Slams, both last year at Wimbledon and the US Open, but each match went three sets.

“I was expecting a very hard ball from (Mika), but I don’t know if it was the weather conditions or not but it wasn’t coming as fast as I was thinking,” Sonobe said. “I couldn’t adjust to that as well.”

The first set of the final was close, with each player showing some nerves. But at 3-all, Stojsavljevic broke serve at 15, giving her the first advantage.

She then consolidated the break as Sonobe had trouble with the Brit’s powerful backhand. A backhand crosscourt winner on set point gave Stojsavljevic the edge.

“I think I just started off trying to be more consistent at the start,” Stojsavljevic said. “Obviously in a final, you want to just get into it a little bit. I think I was consistently getting good depth. It was a bit windy out there, so I think that could have changed things. But, yeah, I think my pace was good enough.”

Now with a beautiful trophy in hand, Stojsavljevic gets to head home.

Hopefully not to math class, though.

“Yeah, I hate math,” she said, smiling. "Not sure (of my schedule yet), but I'm sure it will be pretty intense.”

It can’t be more intense than what she just went through, certainly.

In the girls' doubles final, history was made as Malak El Allami became the first Moroccan girl to win a Grand Slam title, partnering with Norway’s Emily Sartz-Lunde to defeat Julie Pastikova of Czechia and Julia Stusek of Germany, 6-2, 4-6, 10-6.

Sartz-Lunde, a freshman at University of Michigan, and El Allami, a first-year student at Columbia, recovered from the second-set disappointment to grab the first Slam championship for each.

It’s also the first junior Grand Slam title for a Norwegian girl.

“It’s an honour and I’m very proud of this,” El Allami said. “I hope that it encourages people back home to keep dreaming big, and working hard to represent Morocco at the highest stages, and do what they love most, and make everyone proud.”

“I kept telling myself the last tiebreak was to 20 points, so I felt like I had plenty of time to come back if we lost a point,” Sartz-Lunde said with a laugh. “I love playing with her and I had confidence we were going to win, the whole time.”