NASHVILLE (AP) — Tennessee lawmakers on Wednesday tweaked a sweeping voucher proposal to ensure schoolchildren living in the country illegally are prohibited from accessing the program.

The change comes just days after an anti-immigration group came out against the original structure of the bill, arguing it would result in school vouchers for "illegal aliens." However, the amendment also has sparked unease among some Republicans about possible legal concerns.

Under the latest version, families would have to provide a birth certificate, driver's license, passport or some other sort of government documentation for their children participating in the education savings account plan.

"The compelling reason is because ... people have asked for accountability," said Rep. Bill Dunn, a Republican from Knoxville sponsoring the bill. "We have to have an individual with certain identification who can be tracked."

Education savings accounts are different from a traditional school voucher, which allows public dollars to be spent on private schools. Instead, the accounts can be used more liberally because families can use the public funds to pay for not only tuition but also school supplies, transportation, college savings and other approved expenses.

The bill is a key initiative of Gov. Bill Lee and has won support from top Republican officials emboldened after the newly elected governor campaigned heavily on expanding school choice in Tennessee.

Yet the state's teachers union warned that having school districts in charge of verifying students' documentation may be illegal, citing a 1982 U.S. Supreme Court ruling that states can't deny students a free public education because of immigration status.

Opponents argue schools are only allowed to ask for documents that prove the student lives in the district — where a utility bill could suffice — but not for documents that would discourage immigrant families from enrolling in schools.

"I think it makes the law constitutionally suspect," said Rep. Jim Coley, a Republican from Bartlett, who voted against the measure during Wednesday's committee meeting.

Legislative attorney Kasey Washburn told the panel the issue would need to be settled in court because she was unaware of any education savings account rulings.

The House Education Committee ultimately voted 14-9 to advance the bill Wednesday. It still must clear several committees before it can hit the House floor, but Wednesday's meeting was considered a key win despite some Republican pushback.

The proposal is expected to cost at least $125 million over five years but could end up much higher depending on enrollment. Parents of students in certain low-performing school districts could receive up to $7,300 in state funds, but they would need to have incomes below the federal poverty level.

Participation would be limited to 5,000 students in school year 2021-2022. The cap would increase by 2,500 students if the enrollment maximum is met in the following year and 10,000 students during the third year.

Currently, five states allow some sort of ESA: Arizona, Florida, Mississippi, Tennessee and North Carolina. The Nevada Supreme Court struck down its state's law after ruling that the funding mechanism was unconstitutional.

In Tennessee, the existing program is fairly small. Parents of students with certain disabilities can withdraw their children from public school and then receive up to $6,000 to pay for private educational services.