Letting Title I dollars for disadvantaged students follow them to the public school of their choice would end up diluting the program’s focus on children in poverty, according to an analysis by the Center for American Progress, a think tank closely associated with the Obama administration.

The policy, called Title I portability, is included in both the House and Senate GOP proposals to rewrite the No Child Left Behind Act. Unlike in other portability proposals, including one from Mitt Romney, the GOP nominee for president in 2012, the money would only be available for public schools, not private schools.

And, under both pieces of legislation, states would get to decide whether or not to allow Title I funds to follow children. Most would probably opt to keep Title I the way it is, Mike Griffith, a very smart school finance analyst at the Education Commission of the States, told me. He expects that only a few school choice die-hards (think Arizona or Florida) might be interested.

But if all states decided to go for the new flexibility, the results would be pretty grim for the poorest schools, the CAP analysis says. Right now, schools with high concentrations of poverty receive a greater share of Title I money than schools with fewer poor kids. That would change under the bill put forth by Sen. Lamar Alexander, R-Tenn., the chairman of the Senate education committee, according to CAP’s analysis of the Senate proposal.

Overall, districts with high concentrations of poverty could lose an average of around $85 per student, with some districts at risk of losing hundreds of dollars more per student, CAP found. And on average, the most affluent districts could gain more than $290 per student. The provision could mean less money for big urban districts, such as New York and Philadelphia. It would also hurt large suburban districts, such as Fairfax County in Virginia, CAP found.

Why include the Title I portability language at all? It seems like Republican leaders on the House and Senate education panel are looking to offer something akin to private school vouchers, which some folks in their party love, without completely alienating education advocates, who don’t like portability at all, but would really, really hate to see federal funds diverted to private schools.