There are no studies defining when kids should be screened for cholesterol, yet there are accepted standards published by the American Academy of Pediatrics and published in the journal, Pediatrics, proclaiming that kids should be screened beginning at age 2 according to the UCSF Department of Epidemiology and Biostatistics.
The reasoning for this recommendation is that there is an epidemic of obesity and type 2 diabetes that leads to dyslipidemias that we should know about. However, you really don't need a blood test to specifically identify these children; you can look at them and see who is overweight! This simple approach would save billions in screening costs and save making a diagnosis of dyslipidemia that will likely stay with each child for their entire life.