The average Gen Z-er is just finishing up third grade right now.
That sounds about right. They were born in 2010 and are nine years old now. According to the US Census, Generation Z includes those born in 2001 or later. I think the US Census cutoff year for Generation Z is more accurate than the classification of Generation Z by the Pew Research Center.
I'm with you on this actually. I vastly prefer the 2001 start, maybe 2000 at the earliest.
Actually we could say that each generation lasts 18 years: 1946-1963, 1964-1981, 1982-1999, 2000-2017, 2018-2035. That way we can say things like "biggest/smallest generation" in a way that isn't completely meaningless.