Conservative lawmakers are trying to reshape President Bush's education plan as it heads to the House floor, pushing a bevy of amendments from private-school vouchers to blocks on birth control.

A leading House Democrat warned that GOP efforts could dissolve the bipartisan support the bill has enjoyed until now.

Bush's plan sailed through the House Education Committee last week as Republicans and Democrats backed a plan that includes annual testing in reading and math for students in grades three through eight.

The bill emerged from the committee without two key Bush proposals, however: vouchers and a set of regulations that essentially give states freedom to spend federal education funds as they wish.

As it stands, the bill goes to the House floor for debate Thursday saying that if a school has failed to improve after a year, its pupils would become eligible to transfer to another public school. After three years, they could use federal funds for private tutoring or transportation to another public school.

Conservative Republicans, who consider vouchers for private school tuition a "safety valve" for students in struggling schools, promised to offer amendments to let a limited number of states try the voucher concept.

"If I were the president for a day, or dictator for a day, we'd have private school vouchers," said Rep. John Boehner, R-Ohio, who chairs the House Education Committee. He said he and House Majority Leader Dick Armey of Texas would introduce a voucher amendment.

Conservatives also were expected to offer other amendments, including one that would bar federal money from schools that offer students "morning-after" birth control pills.

Currently, the House bill would let local school districts spend up to 50 percent of their federal funds essentially as they wish, which supporters say would enable local officials to target money to their greatest needs, whether teacher training or technology.

Conservatives unhappy with the bill want to expand that to 75 percent and to restore a provision, stripped from the House bill, that would let states enjoy similar freedom.

House Democrats said that could wreck the bill's wide bipartisan support.

Rep. George Miller, D-Calif., ranking Democrat on the House committee, said that if conservatives revive the state flexibility provisions, "It's the end of the bipartisan coalition."

Conservatives have grumbled about the bill for weeks. Compromises on flexibility and vouchers, they complain, have taken it far afield from Bush's vision.

"It's very tough to find any GOP person who loves this bill," said Rep. Pete Hoekstra, R-Mich., who planned to introduce the flexibility amendment. "We promised school districts flexibility."

Hoekstra conceded that House leaders probably have enough votes to pass the bill even without the help of 20 to 40 conservative opponents but said the victory would be at the expense of support for other issues, including future appropriations.

The Senate has been debating its version of the bill, on and off, for weeks. There, as in the House, conservatives have been growing restless with the results, particularly as Democrats advance a series of amendments to add spending.

On Wednesday, Senate Majority Leader Trent Lott, R-Miss., said spending levels have "exploded totally out of control" and must be reduced.

A proposal by Democratic Sen. Barbara Boxer of California to increase money for after-school programs won approval, 60-39. But an amendment by another Democrat, Iowa Sen. Tom Harkin, to add $1.6 billion for school construction and modernization failed on a near-party-line vote of 50-49.