The South, where public schools have been considered the most backward in the nation, suddenly is trying to leapfrog its neighbors in quality of public education.

Southern states are in the forefront of such areas of innovation as merit pay, school board accountability, competency requirements for teachers and students and the willingess to pay for it with new tax money.

Virtually every state of the region has undertaken or is about to begin an overhaul of its public education system.

"It's nice to be in the lead on education for a change," Gov. Lamar Alexander (R-Tenn.) told an assenting group of colleagues, who traded notes on education at the Southern Governors' Association meeting here today.

Alexander, who is trying to enact a merit pay plan in his state that would be funded by a one cent sales tax, estimated that he has spent 70 percent of his time on education issues this year.

In Arkansas, where the legislature will convene in special session Tuesday to consider a comprehensive education package proposed by Gov. Bill Clinton (D), the governor said he has been doing little else for the past five months.

"A lot of people are wondering why we're doing so much of this in the southern states," Clinton said. "I have a theory . . . . All of us suspect that the changing nature of the economy permits the South, for the first time, if we make the right sacrifices, if we quit making excuses, to bring our own people to or above the national average in income, because of the way the jobs are moving. That's my own not-so-secret hope."

"Our economic development will succeed or fail on the strength of our schools," seconded Gov. Charles S. Robb (D-Va.).

Clinton's proposed package, like so many others in the South, is part catchup and part innovation.

It would make kindergarten mandatory for the first time in Arkansas and reduce class size to 20 in grades K through three by 1987. It would mandate that all administrators and teachers take job-related competency tests and provide interest-free loans for remedial study to teachers who fail the test, but revoke certification for teachers who fail repeatedly.

The package also would establish statewide competency tests at various grade levels for students, and provide for decertification of a school or entire school districts where less than 85 percent of the students pass the test.

It would be funded by a $170 million tax package. Clinton said public opinion polls indicate that 63 percent of the voters of his state will support tax increases for education as long as it is accompanied by some form of accountability.

Despite sweeping overhauls of public education in the past two years in Mississippi, Florida and Virginia, the road to reform has not been easy.

In Texas, Gov. Mark White's (D) proposal for a 24 percent increase in teacher pay stalled in the legislature this summer. Gov. Richard W. Riley (D) of South Carolina lost a one-cent sales tax increase proposal by three votes. Gov. William F. Winter (D) in Mississippi got his package passed on the third try.

"Getting educational reform can be like moving molasses," said Alexander, whose merit pay plan and one-cent sales tax were killed last spring after a heavy lobbying effort by the National Education Association.

Alexander has since gone to the voters with a direct mail and paid media campaign, and he will try again in the legislature next year.

In addition to merit pay, Alexander's plan will embrace the idea that "every child can learn . . . . We want to take our best teachers, offer them more pay for 11 and 12 months contracts, and have them work in the summer months in small classes with students who have fallen behind."