The debate over whether to maintain annual testing requirements has garnered the most attention as Congress works to overhaul the No Child Left Behind law. But it’s becoming very clear that the real obstacle is how a forthcoming rewrite deals with Title I dollars for low-income students.

The White House unveiled a report on Friday that blasts language in the Republican-backed NCLB rewrite moving through the House that would allow Title I dollars for low-income students to follow them to the public schools of their choice, including charter schools.

It argued in the report that the Title I portability provision “would allow states to spread Title I funds thinly across the wealthiest districts, doing less good, while sending less funding to many districts that need it most.”

The report also criticized the House measure over locking in pre-sequester spending levels and its elimination of maintenance of effort, which requires school districts and states to keep up their own spending at a certain level in order to tap federal dollars.

But the bulk of the report focused on the ramifications of the Title I changes, leading reporters on a press call to ask Cecilia Muñoz, the director of the White House Domestic Policy Council, if a NCLB rewrite with this Title I portability language would be vetoed by President Barack Obama.

As you might expect, Muñoz ducked the question (twice, in fact), saying instead that the White House is hopeful negotiations in the Senate between education committee Chairman Lamar Alexander, R-Tenn., and ranking member Patty Murray, D-Wash., will yield a bipartisan bill that reflect the president’s core principles for reauthorizing the law.

Those negotiations, however, are occurring after Alexander has already planted his flag for rewriting NCLB with a discussion draft that includes—surprise, surprise—Title I portability.

What’s more, Republicans in both chambers plan to push the portability of those federal dollars further during floor debate by offering amendments that would allow Title I money to also be used for private schools, a move that would increasingly dilute the amount of funding going to low-income school districts.

It’s easy to understand why the White House won’t yet commit to a veto threat at this point. It doesn’t want to undermine negotiations that could (in theory) produce a proposal with a semblance of bipartisanship in it. Muñoz noted that White House officials are speaking regularly to senators on both sides of the aisle.

But that didn’t stop her from noting that “portability determines the winners and losers here” when explaining how the Republican-backed NCLB overhaul in the House would impact funding levels for school districts.

With that being said, we’re expecting an official veto threat on the House bill to arrive in our inboxes the week of Feb. 24, when lawmakers are slated to debate the measure on the chamber floor.