Assembly Speaker Karen Bass’ office has been mum  about whatever progress there has been in resolving differences over SBX5-4, the compromise Race to the Top bill that the Senate passed last week.

One part of the bill that needs fleshing out through amendments involves a significant expansion of parental choice that Gov. Schwarzenegger  and Sen. Gloria Romero have pushed hard for.

Romero’s original bill, which died in the Assembly, would have given parents in the lowest 30 percent performing schools the right to transfer to a better school in another school district. The current bill scales back that right to the bottom tenth. But it still marks a major shift in state policy and philosophy – and a victory for Los Angeles parent groups that made their voices heard in Sacramento.

Just last summer, the advocacy group EdVoice looked like it was fighting a losing battle to renew a strictly voluntary parental choice program affecting only 5,000 students attending schools in districts that volunteered to take them.

Now, open enrollment will expand to theoretically hundreds of thousands of children. And all districts with space  for more students will be required to accept children from the worst schools, based on a lottery system.

Romero sold open enrollment as a civil rights issue, providing families stuck in failing schools the right to a good education. And she’s right.

But the language of the bill is largely aspirational. It lacks details on how the program would work. Sen. Joe Simitian, while voting for the bill, raised serious questions that need answers. Among them:

• How would be reimbursement work? Would the full tuition follow the student to the receiving district, or would it be partial? Would the sending district get the tuition for one more year after the student leaves, to soften the impact, as currently happens in declining enrollment districts?

• Could a district claim financial hardship and deny an out-of-district admission? How would that be defined?

• What is the definition of available space? If a school technically has room for more students, but has limits on class size, would it have to abandon small classes to accommodate more students? Or reopen closed schools?

• Would largely wealthy basic-aid districts, like Palo Alto and Woodside, which are funded through property taxes, receive any state reimbursement?

• What would be the process for appealing a district’s denial of a transfer?

• Would schools be able to reserve spots for late enrollments from students whom they know will move into a neighborhood? Could districts that build new schools, designed to accommodate projected growth over several years,  be able to reserve space for the future?

These are not minor questions. Unless there are some answers written into the bill,  wealthy districts with good schools will fight opening up their doors to outsiders, and opportunities for low-income students will be squandered in litigation for years.