There's no reason that the four basic operations cannot be learned by any normal child by the end of second grade. Multiplication is repeated addition, and division can be taught in a number of easy to learn ways, including as repeated subtraction. Singapore Math seems to be at least a year ahead of the scope and sequence of most U.S. curriculums when compared by grade level, but it doesn't have to be that way.
Yep - both are in the syllabus for the first term of the third year in DS's unselective school. Children start school at between 4.5 and 5.5 here, so this is marginally "earlier" than the first term of 2nd grade, I think. Specifically:
Recognise multiplication as repeated addition
Recognise division as repeated subtraction
The relationship between multiplication and division
The x2 multiplication table and facts
Division by 2 as grouping in twos
Recognise division as the reverse of multiplication
Recognise doubling as twice a number, halving as
reverse of doubling
Recognise unit fractions, find 1/2,1/3,1/4 of amounts
Add and subtract multiples of 5 and 10
