During his HSC, while his friends were doing last-minute study for their next exam, Max Samengo was on his way to the Gold Coast.

He was one of about 5000 Australians who juggled both the HSC and the US' university application process, which includes sitting either the SAT or ACT exams, in the hope of studying in the US after year 12.

"Two days before the modern history exam I was in the Gold Coast doing the ACT exams because I booked it so late that all the Sydney testing centres were booked out," said Mr Samengo, 18, who graduated from The Scots College, in Sydney, last year.

The number of Australians studying in the US has increased steadily in recent years, with nearly 4910 students enrolled in US institutions last year, up from 3850 in 2012.

While Mr Samengo said that doing an external exam during the HSC might have affected his marks, the gamble paid off. He has now been accepted into the University of Chicago.

"I found out a week after ATARs came out. I was absolutely more nervous about Chicago than the ATAR," he said.

Mr Samengo said the University of Chicago's core curriculum model, which requires students to study a mix of science and humanities subjects, will give him a chance to explore his interests in both physics and literature before having to choose a major.

"I've wanted to go overseas for the last four or five years of high school. I'm excited to learn that sort of breadth of content," he said.

He said that, while the ACT exam was much easier than the HSC, he would start the process much earlier if he had to do it again.

"If you think about it from year 9 onwards, you can focus on particular extra-curricular activities and you wouldn't need to do the testing in the middle of the HSC," he said.

Jamie Beaton, co-founder of coaching company Crimson Education, which also helps students with the application process to study abroad, said many of the top universities - including Harvard, Princeton and Yale - look at transcripts and extra-curriculars from year 9 onwards.

"I recommend that students start thinking about possible options for their university study at around 13 or 14," he said.

"I would [also] advise students to do 10 extra-curriculars over the course of four years. These can include anything from one-off conferences to overseas trips for a sporting delegation to national debating representation."

Christopher Zylstra, 18, who also went to Scots College and has been accepted into the University of Pennsylvania, said he has known he wanted to go overseas for a few years and started the application process when he was in year 11.

"It was tough but fortunately I did have a bit of time between the HSC and the American exams," he said.  "It's difficult because you can't get much help for the US ones because no one else is doing it."

Universities in the US begin their year in August and many students receive offers in March after Australian universities begin.

"I get a half gap year, I'm really looking forward to meeting new people and getting to experience something new," he said.

By Pallavi Singhal, Originally published in the Sydney Morning Herald