Place value subsequence

Note that Khan Academy covers place value of whole numbers up to thousands, and decimal numbers up to thousandths. Strangely, Khan Academy doesn't cover place value at all in 3rd grade, and so there is a gap between place value to hundreds in 2nd grade, and place value to hundred thousands in 4th grade. Thus, I infer that place value to thousands should occur in 3rd grade. I also think place value beyond hundred thousands should occur in 5th grade, and thus, decimal place value can also be taught for arbitrary place values, such as millionths, billionths, etc.