Lawmakers have made some valuable changes to the law covering public charter schools but have punted on the most important issue.

Charters are independently-operated, publicly funded schools that are alternatives to conventional public schools. Gov. Tom Corbett and legislative Republicans have pushed hard for the expansion of charter schools, believing that they will improve education and lower costs by making conventional schools compete for students.

So far, charters have operated with only a fraction of the accountability of conventional public schools, even though they are publicly funded.

The bill will require independent annual audits of charter schools and commission the state Board of Education to create charter school performance standards. Charters must have teacher evaluation systems. It will strengthen specific ethics standards for charter school administrators.

In furtherance of their advocacy for charters, the governor and lawmakers have made it easier for charter schools, which must be approved by local school boards, to appeal denials to a state Charter School Appeal Board.

Now, charters receive a per-student tuition payment from local school districts. Charters often complain that the districts deliberately delay payments. The new law requires the state Department of Education to pay charters directly.

The bill fails to address the most important issue - charter funding. Tuition is based on the cost-per-student in each student's home district, regardless of the charter school's actual costs. Districts' costs typically are higher. As reported by Auditor General Jack Wagner, some charters - especially Internet-based schools that have no buildings - have been able to accumulate surpluses far beyond that allowed for districts.

The new law limits the amounts of surpluses that charters may accumulate but does not address the funding formula, which should be based on actual cost.

Until the Legislature tightens the funding formula, lawmakers who favor charters won't be able to credibly claim that charters offer better education at lower cost.