Sen. Gloria Romero’s willingness to compromise on the most controversial parental choice provision may have saved her parents rights bill – SBX5-4 – though with not one vote to spare in a critical Assembly vote Tuesday.

Students trapped in persistently bad schools will now have the right to choose an academically better school in another school district. This marks a fundamental shift in school governance. But, during hearings, legislators and lobbyists for school boards and teachers had less of a problem with principle than with the details of how open enrollment would work. The bill lacked specifics.

Amendments satisfied some concerns – and also weakened the program’s potential impact. But a cautious approach makes sense, considering there will unanticipated effects, and details will need to be worked out. Small low-income school districts are particularly worried about the financial repercussions.

Here’s how open enrollment would work:

Instead of applying to the lowest scoring 3,000 schools, as Romero had proposed, it will apply to 1,000 schools designated by the superintendent of instruction. That will probably correspond with the lowest decile of schools, as measured by API scores, but there may be reasons why a few shouldn’t be on the list.

Critics complained that charter schools will be exempted from on the list. But parents already exercised choice in sending children to charter schools and can pull them any time.

Anti-discrimination clauses were tightened to prevent receiving districts from cherry-picking students.

A maximum of 10 percent of a district’s schools will be subject to open enrollment, easing concerns of a mass exodus of students.

Funding has been clarified to lessen financial impacts. In the standard case, in which a student leaves a revenue-limit district for another revenue-limit district, both the sending district and the receiving district will get full tuition (ADA) for the student the first year. In subsequent years, the receiving district will get the student’s ADA.

In the case where a student transfers to a basic aid district, the sending district will get ADA the first year. Starting in the second year, the basic aid district will receive only 70 percent of the child’s ADA (on the assumption that the sending district still has fixed costs associated with the student). Basic aid districts, which comprise about 10 percent of the state, are concentrated in wealthy parts of the Bay Area and are funded strictly through property taxes.

The equivalent Title 1 money, which is federal aid for low-income students, will stay with the sending district, since it’s calculated on a different basis. However,  the child’s parent can demand that a portion of it be used for transportation to the new district.

Receiving districts will be able to set reasonable conditions for accepting out of district students, and these will withstand a legal challenge as long as the criteria weren’t made arbitrarily.  Districts can cite capacity limits in a school or magnet program, and can cite “adverse financial impacts” – a broad category. They also could give priority to siblings of students enrolled and give some priority to intradistrict transfers.

So receiving districts will have leeway to keep kids from other bad schools out; that was the price of legislative compromise.

What will ultimately make it work will be financial incentives: increased per pupil funding for low-income children and English learners and school-based budgeting. The latter would give an under-enrolled school latitude to invite in kids from surrounding districts. Both ideas were raised by Governor’s Committee on Education Excellence.

For now, the principle of open enrollment has been established. Over time, when the full consequences become known and problems fixed, the program can be broadened.