We use U.S. edition of the workbooks (not the Standards Ed but the regular one). I think the placement tests work quite well. If your daughter has problem with one of the section, let's say she cannot calculate area, do only that section and then move onto the next level. I would suggest that you get the Challenging Word Problems workbook too. It goes more into depth and where the regular workbook (which we do use) is quite easy for DS6 he has to really think about some of the challenging word problems.
As questions said I bought the Singapore version of HeyMath! since it gives me more years for the same price.
