Your child need not know Mandarin. But he will definitely benefit with a strong foundation from the core subjects like Maths & Science and some moral education. Also, he will make a lot of Singapore friends.
By the time he gets back to his own country, he will definitely be in a very strong position academically.
See the testimony of a top U.S student from Colorado who had a perfect score in the U.S college entrance exam and attributed this partly to his training in Singapore:
http://www.google.com/search?q=cache:www.sg/flavour/bulletin/bb-edu04.html+singapore,U.S+student,top&hl=en
BTW, the Math & Science standard in the primary/secondary schools were tested in 1995/97 and again repeated in 1999 in an American initiated test involving some 40 over countries worldwide called the TIMSS
(Third International Math & Science Study)
{See the ranking chart below of all participating countries}
Singapore top the Math & Science in 1995 and
the tests repeated in 1999 shows Singapore top the Math & was runners up by one point to Korea in Science.
There is another study comparing the "pick of the crop" from U.S schools against the ROW (rest of the world). See the comments from the APA in U. of Missouri/Columbia: http://www.apa.org/ed/geary.html
".. only about 1 out of 100 U.S. students scored as well as the average student in the top-ranked nation, Singapore."
More importantly is the consistency in the Singapore Schools producing the largest number of top math & science students in all these tests ..and its not rote learning that is measured...and this is across the board as the student sample is representative of all abilities in the local schools.
The local schools are able to help build mathematical and other important concepts in the young. You will be surprised by the resources in the local schools. The local teachers have also been highly commented in one of these studies.
As for Sports & co curricular activities, there are now a wide choice to choose from. Some schools offer sea sports as well. There are also good IT programmes in the primary/secondary schools.
Some schools/homeschoolers in the U.S are using the Singapore textbooks for Math. & Science.
If you are interested, the maths/science standard of the participating countries (including Australia,Canada, UK and Japan) are ranked in:
1999 study:
http://nces.ed.gov/timss/timss-r/figure_1.html
Also mentioned is the fact about the relevance of teacher qualifications (mentioned in the previous study about Singapore - that the majority of Singapore teachers are qualified for the subject they specialised in the University):
http://nces.ed.gov/timss/timss-r/highlights.asp#4
Despite what the media & generally what has been said about the Singapore Education system, it still produces the best primary/secondary students...to be top rank in the world, repeatedly.
If you are looking for a good academic grounding for your child, send him/her to a good local school...
regards