“They are saying ” I want my kid to be the best in the class”.
That is absolutely not true, at least not in every case. We held back one of our kids in kindergarten for a second year because, as the youngest kid, he was behind, socially and physically. In kindergarten it makes no difference, but in later grades it does. He thrived in the next year, when he was from among the oldest. Parents want their child to be able to hold their own among their classmates.