Research shows that 4-1/2-year-olds in class with 5-year-olds are at a disadvantage that can stay with them, Mr. Simitian said in a statement.
About a quarter of California children start kindergarten before they're 5, and most states have earlier cut-off dates, Mr. Simitian said.
The change has the "outspoken" support of educators in San Mateo, Santa Clara and Santa Cruz counties, Mr. Simitian said.
Also supporting the bill: the Legislative Analyst's Office, the California Performance Review, and the Governor's Committee on Education Excellence, he said.
"Almost every child who comes to me for reading support has a fall birthday," said Palo Alto reading specialist Natalie Bivas, who was quoted in the statement. "They don't catch up somehow down the line. Instead, they end up on everyone's radar. By third grade, teachers start asking me why we didn't hold these children back. By then, we're discussing a special education intervention."
SB 1381, which would be phased in over three years starting in 2012, would save the state about $700 million annually and $9.1 billion over 13 years, Mr. Simitian said.
About half the money would go to "quality preschool programs" for the affected children and the rest toward reducing the state's budget deficit, Mr. Simitian said.