It is useful but not very useful.
These chinese kids are very greatful but they do not select maths as their career. That why "那些解决世界数学难题，或发现数学问题的数学家，有几个是奥数竞赛的优胜者".
The Russia genius mathematicians ( sorry forget his name) got three times gold medal when he was teenage.
Now he is the best in the world.
奥数赛，中国学生令韩国学生直冒冷汗