But not for Shay Kerry. He plays both and is making great strides in the two sports.
Kerry started out playing football when he lived in Folkestone in England.
He was good enough to get into the Millwall Football Club's system in London and played for that club's junior sides.
But dreams of wearing the Millwall jersey were shunted aside when, five years ago, his family moved to New Zealand.
They initially lived in Napier for about 18 months before moving south to Dunedin.
Kerry kept playing football and was good enough to make a New Zealand development side which went to Singapore and achieved some top results.
He left Taieri College at the start of last year to take up a football scholarship at Otago Boys' High School, and quickly became a member of the school's First XI, a dominant centre-half in the side.
At the end of the last winter, Otago Boys' High School First XV coach Ryan Martin asked Kerry if he wanted to have a game of rugby.
Standing 1.98m, and weighing in at just under 100kg, Kerry took to rugby like a duck to water.
Slotted in at lock, he was impressive enough in a couple of games to make the Otago under-16 side to play in the South Island tournament.
This year, with school football games played on Wednesday and rugby matches on Saturday, the year 13 pupil could do the double and has managed to play both so far.
The First XI has won all its games bar a match against Christchurch Boys' High School, when Kerry did not play, while the First XV is yet to lose a game.
He trained with his rugby team three days a week and with his football team two mornings a week, and tried to go to football training after rugby practice finished.
Rugby had come to him naturally, and he enjoyed the camaraderie of the game.
But which did he prefer, and which was harder?
"You probably do more running in soccer, though it is completely different here than it was back in England. Rugby is harder physically in terms of taking the knocks and the contacts," he said.
"Then there is more sort of short running and a lot of stops and starts. We are doing well in both competitions so it is a lot of fun."
He admitted homework was sometimes a problem but he somehow found the time.
He does not know which sport will dominate his future.
If he went back to the United Kingdom, he would play football but rugby may be his sport if he stays in New Zealand.
FAST LANE
Name: Shay Kerry
Age: 17
School: Otago Boys' High School
Achievements
Football: Otago Boys' High School First XI, Otago age group teams, New Zealand under-15 development team
Rugby: Otago Boys High School First XV, Otago under-16
