It's hard to argue against the troubling fact that thousands of students are trapped in poorly performing public schools. But a proposed voucher bill in Harrisburg has serious flaws and raises concerns.

For starters, the measure lacks both academic and financial accountability. It would siphon millions of dollars away from public schools at a time when education funding faces deep cuts.

The Senate Education Committee is expected to vote on the voucher bill this week. So far, even Gov. Corbett, who has expressed support for vouchers, hasn't endorsed the measure.

Opponents estimate the plan would cost $100 million the first year, and tens of millions of dollars more as the program expands in the coming years.

Sen. Jeffrey Piccola (R., Dauphin), one of its cosponsors, puts the cost at $50 million - still a hefty sum at a time when public schools face cuts in state funding and lawmakers who are reluctant to raise taxes.

No doubt, the voucher proposal is well-intentioned. It is designed to help mainly poor students who are stuck in lousy schools. The measure would give state-funded vouchers to low-income students in Pennsylvania's 144 lowest-performing schools. The scholarship would equal the amount the state pays a district to educate a child.

Most of the eligible schools are in Philadelphia. The district could lose up to $40 million in the first year if a small fraction of the 55,000 eligible students leave.

By the third year, the bill would allow any student in a private or parochial school who meets the income requirements to get a voucher. How does that help students escape bad public schools? Should the government pay for kids already in private schools?

The voucher also would increase existing tax credits offered to companies that contribute to private-school scholarships from $75 million to $100 million. The arrangement is a clever way for the state to divert tax dollars to pay for vouchers.

With an average "opportunity scholarship" of $9,000 in hand, highly motivated parents could send their children to a better-performing public school or a private school. At least in theory. But it's not that simple in practice.

There are no guarantees a private or parochial school will accept every student who shows up with a voucher, or that there are enough seats to meet the need. Unlike public schools, the private schools can accept or reject any student.

The bill also falls short in not providing a way to hold private schools accountable for the academic results. Nor is transparency mandated on how tax dollars are spent.

Even with a voucher, an education at an expensive private school could still remain out of reach for some families. At the same time, public schools will have less money to educate the remaining students, but many of the same fixed costs.

The bill offers a sobering dose of reality that vouchers alone are not the panacea to make the public schools better. Research is mixed on how much vouchers improve overall student performance. The reality is, the majority of students will remain in their neighborhood schools - even with a voucher program.

A better course is to invest public dollars in public education, while holding teachers and districts accountable, and even closing the worst schools.