For the past few years, mental arithmatics has been gaining popularity in Singapore. I also noticed the same trend happening in Indonesia. Starting from pre-school age (kindergarten), children were attending enrichment classes teaching the subject.
I have tried myself to learn the technique. Being a math geek when I was younger, I found it very interesting and useful. The method really simplifies the addition and substraction without using pen and paper.
I don't know how it would affect the performance in school. Either it will motivate the children further when they can handle the subject or the children may feel overwhelmed with additional pressure on studying especially if they already have few other enrichment courses to attend.
No matter how the result maybe, it is important to have a balance coupled with individual's interest.
