Yoder told the Senate education committee on Wednesday that the change would prevent families from having to spend a year juggling their children between public and private schools when they've already decided on private school long term.
Christa Runion of Indianapolis told the committee that her 9-year-old daughter is now attending a Catholic school in Greenwood on a voucher after spending a year in the Perry Township schools, where her 6-year-old son is now in kindergarten. Runion said she spends about two hours a day picking up her children at different schools.
She said her daughter has had to miss out on after-school activities because of the public school requirement for her son, who will be attending the same parochial school as his sister next year.
Yoder said children forced to start in public school before going to private school face being taken away from their friends when they change schools.
"I just do not see how it is helpful for that child," he said.
Indiana has the country's largest voucher program, spending about $36 million on subsidies to low- and moderate-income families toward sending about 9,100 children to private schools this year.
The state Supreme Court is weighing the legality of the program after hearing arguments in November from opponents that virtually all of the voucher money goes to schools whose primary purpose is to promote the teachings of their affiliated churches.
Sen. Luke Kenley, R-Noblesville, said during Wednesday's committee meeting that he thought making a sibling exception represented a "fundamental change" to the agreement reached during the 2011 debate on the program that public schools should have a chance to first win over parents.
Kenley is chairman of the Senate Appropriations Committee, which would have to consider the voucher expansion if it clears the education committee in a vote that could happen next week.
Kenley said the sibling exemption could add millions of dollars in additional costs for the voucher program and change the premise on how students qualify.
"It seems to me we are maybe breaking down that voucher system," he said.
Yoder countered that it was unfair to require low-income families receiving vouchers to go through more one-year public school periods for their children.
"These are not kids who are going to stay in the public schools," Yoder said. "The family has already made that decision."
Runion, the Indianapolis mother, said that ideally all children could be eligible for vouchers without first spending time in public schools, but that she understood that the state might not be able to afford such a step.
"Even when I was a young child in a parochial school I didn't feel that it was fair that my parents had to struggle to send me to a private school when their tax dollars were going to the public schools," she said.