Parents haven't even begun to realize their new power under the No Child Left Behind Act, pushed by President George W. Bush and approved by Congress last year.

Parents whose children attend schools that receive federal Title I money (there are 65 in Prince George's County) will be notified if their child has a teacher who is not properly certified or qualified, and that teacher is in the classroom for at least four weeks. The first such letters should go out fairly soon in Prince George's County.

Maybe that wouldn't seem revolutionary to someone who hasn't spent much time around schools, but it is.

"It will make some waves," schools chief Iris T. Metts told me.

A typical situation is a Title I classroom where a teacher has a provisional certification or where a long-term substitute has been hired to fill in for a teacher who is ill. About 19 percent of all teachers in Prince George's County have a provisional certification.

Parents will learn by letter of such situations after the teacher has been on the job four weeks. In addition, parents in any Title I school will be able to find out the teachers' qualifications -- their major in college and their level of state certification, for example.

These are two ways the new law offers information to parents in hopes of getting them to push for improved schools.

Ron Peiffer, assistant state superintendent for school and community outreach, said he recently met a parent from Howard County who had received a letter that her child had had a long-term substitute for more than four weeks. She went to the school, asked about credentials and was satisfied that the teacher would be suitable for her child.

"That is what is supposed to happen," Peiffer told me.

Parents don't have to assume that a substitute teacher or a teacher with provisional certification is unqualified or "bad." Sometimes certification is provisional becausethe teacher recently moved from a state with different certification requirements and is working to fill a small gap, such as by taking a couple of courses. Sometimes highly qualified people work as substitutes to maintain flexibility in their schedules.

But parents are perfectly justified in looking closely at a provisionally certified or substitute teacher. They should ask the teacher for examples of how the child has progressed in the time they have had together. If the child began writing three-word sentences and now writes paragraphs of several sentences, that would be evidence the teacher is doing a good job.

If parents are not satisfied with what the teacher demonstrates, they have the right to ask that their child be moved to the classroom of a highly qualified teacher. That is because of another provision in the new law that allows parents in Title I schools that are not improving to transfer their children to better-performing schools.

I've used the term "highly qualified" several times now as though it were self-explanatory, but of course it isn't. People who care about education have been struggling for a long time with the question of what constitutes a highly qualified teacher. The U.S. Department of Education now defines the term by saying that new teachers must have a degree in a "core" subject: math, English, foreign language, science or some other academic subject (not simply "elementary education"), and have either full certification or a passing score on the Praxis test, a national instrument used to see whether teachers know something about teaching. Senior teachers must have a satisfactory evaluation on a statewide evaluation system or meet the above requirements.

The rub for teachers already working in Maryland is that it, like most other states, does not have a statewide evaluation system. So it looks as if fully certified teachers who have been teaching for some time might have to get a degree in a core subject, if they don't have one, to comply with the new law.

Being "highly qualified" as defined above is no guarantee that someone is a good teacher. But it's a start.

"It's no guarantee, but let's back up and look at the evidence," Peiffer said. "The most experienced and most qualified teachers are in the schools with the least number of needs and the least number of challenges. The schools with a high number of challenges and needs generally have the teachers with the least experienced and least qualified teachers, and this is a practice that has been going on for 100 years."

Many experts have long noted that teaching is one of the few professions where we put our most expert practitioners where they are least needed, and give our rawest and newest recruits the biggest challenges. No beginning engineer would be allowed to build the new Woodrow Wilson bridge. Yet our neediest kids get our newest and least qualified teachers.

The new law is at least an attempt to rectify that situation by giving parents the power of information and the questions to ask.

"It's medicine," is the way Metts described the law.

"The patient is sick, there's no question about that. We have historically had a problem with certification. The solution, of course, is money."

Even people who support the new law worry that it is actually a covert attempt to destroy public schools by giving parents the right to pull their kids from classrooms and schools and, ultimately (if the voucher folks get their way), the public school system altogether. That's the danger. But I am hoping parents in needy schools will live up to the challenge and pull together with their schools to help recruit and attract highly qualified teachers.

"It's how you use that information to improve the system," Metts said.

There are very needy schools and school districts where parents attend job fairs to demonstrate to teaching applicants that even if the kids are needy, the community is warm and welcoming and will support them in bringing kids to high levels of achievement.

Another way parents can help is to examine the school improvement plan -- one is supposed to be publicly available at every school -- and make sure it includes incentivesfor experienced teachers to come and stay, such as high-quality professional development activities and built-in time for teachers to meet with their colleagues to talk about lesson plans and students' individual needs.

(My fantasy is that parents make sure every needy school has clerical support for teachers so that they can spend their time teaching instead of photocopying -- but I'm afraid that is destined to remain a fantasy for at least a little while longer).

This is just the beginning of the impact of the new law. It is very powerful legislation. I'm with Metts when she uses a medical analogy: The new law will either kill or cure public schools. It's up to us which it will be.

Homeroom appears every other week. Send questions, opinions and issues that you would like to see discussed to Homeroom, The Washington Post, Prince George's Extra, 14402 Old Mill Rd., Suite 201, Upper Marlboro, Md. 20072. The fax number is 301-952-1397; the e-mail address is homeroom@washpost.com. To see previous columns, go to www.washingtonpost.com, click on the Education page and look for Homeroom under Education Columnists.