There are free pre-tests on their website: http://www.singaporemath.com/Placement_s/12.htm .

Keep in mind that Singapore Math is 1/2 to 1 year ahead of typical American math. So a typical 3rd grader working at grade level starting the year now would start at 2A or 2B, depending. Obviously kids ahead of the curriculum would start at a higher level.

Kriston