My thought having had kids in ps, a public charter school, hsed, and one now doing EPGY math, is that the schools don't wait until 3rd-5th grade to introduce the concept of fractions, but do wait until that point to do a lot of work with them -- LCM, reducing, making improper fractions into mixed #s, etc.
Dd9 is a 4th grader and working very slowly through EPGY as a supplement. She's in the 5th grade on EPGY at this point. There was
a lot of work on fractions in EPGY 4th grade and the ps covers a lot of fraction stuff in late 4th as well. One of my friends tells me that 5th grade math also covers quite a bit of fractions in school settings. I do recall my kids getting basics of what fractions were (1/2 of a pizza, 1/3 of an apple, etc.) by at least 1st grade, though. (eta: by "getting" the basics of what fractions were, I don't mean that it took them until 1st grade to understand the concept of 1/2, but that they were given that info in math classes by 1st grade at the latest.)
