President Bush on Saturday lamented recent "shocking acts of violence" in schools, and promised his administration will do what it can to keep centers of learning safe for students.

The White House is convening a conference on school safety Tuesday. Federal officials, school workers, parents, law enforcement officials and other experts are to gather in Chevy Chase, Md., a Washington suburb noted for exceptional schools.

The conference is being hosted by Attorney General Alberto Gonzales and Education Secretary Margaret Spellings. Bush and his wife, Laura, are expected to attend part of it.

"Our goal is clear: Children and teachers should never fear for their safety when they enter a classroom," the president said in his weekly radio address.

In the past two weeks, three schools in three states have been hit by deadly attacks and several others have faced threats.

A gunman killed himself and five girls Monday at a one-room Amish schoolhouse in Pennsylvania. A 15-year-old Wisconsin student was arrested Friday in the shooting death of his principal. On Sept. 27 a man took six girls hostage in Colorado, sexually assaulting them before fatally shooting one girl and killing himself.

Schools in Virginia, Nebraska, Nevada, Oklahoma, Oregon and Wisconsin have been closed or locked down in the past week because of threats of violence or guns on campus.

"Laura and I are praying for the victims and their families, and we extend our sympathies to them and to the communities that have been devastated by these attacks," the president said.

Bush also pushed for reauthorization of the No Child Left Behind law, which he says needs some changes. Under the law, schools that get federal poverty aid and fall short of their yearly progress goals for two straight years must offer transfers to students. After three years of failure, schools must offer low-income parents a choice of tutors.

The law is scheduled to be renewed by Congress next year, but some education observers have speculated it may be bumped until as late as 2009, after the next presidential election.

Leading Democrats backed passage of the law, but they now say Bush has not adequately funded it.

The president outlined a series of ways in which the law could be improved, such as by expanding testing in high schools, an idea he has pitched to Congress for two years. He also said he wants the federal government to pay for 28,000 low-income students across the country to transfer to private schools, and has asked for $100 million to pay for the initiative.

"Thanks to this good law, we are leaving behind the days when schools just shuffled children from grade to grade, whether they learned anything or not," Bush said. "Yet we still have a lot of work to do."