Average teacher salaries nationwide have risen more sharply in the last two years than at any time since the 1950s, when inflation is taken into account, largely because of a major increase in spending on schools by state governments, according to a new report by the National Education Association.

The NEA report says that for the first time the states are contributing slightly more than half of education revenues -- 50.1 percent -- while the share from local taxes, traditionally the largest supporter of public schools, has declined.

Federal spending has dwindled to 6.4 percent of all public education revenues, the NEA said, although the level of federal education spending rose slightly this year.

The major increase in state spending -- 21.2 percent over the last two years -- and a continued decline in inflation have combined to give teachers gains in buying power of about 3.5 percent in 1985 and 1986, the report states.

Per-pupil spending in the schools, after accounting for inflation, also rose substantially, the report said.

"Responsibility for education is shifting more and more to the states," said Mary Hatwood Futrell, president of 1.8 million-member NEA, who released the annual report at a news conference yesterday. "People talk about local responsibility. But when the states pay more, they make more decisions. The states are assuming more and more funding and leadership. But we believe the federal government must remain involved to ensure there is equity."

According to the new report, classroom teachers in District of Columbia schools have an average salary of $33,990 this year, far above the national average of $25,257 and higher than any state except Alaska.

However, teachers in Virginia, whose salaries average $23,382, showed a much greater one-year gain of 9.9 percent. That is one of the steepest increases in the country and reflects the efforts of former governor Charles S. Robb to increase teacher pay.

Even so, total per-pupil spending in Virginia lags more than $1,000 below that in Maryland -- $4,329 to $3,210. Public school spending in the District, $5,020 per student based on average daily attendance, is above that in all but four states. Nationwide average per-pupil spending is $3,677 -- up 6.8 percent this year.

The NEA report, which contains data for the 50 states and the District, does not provide information for individual school systems. In the Washington area, other data shows that Arlington and Alexandria schools have higher per-pupil spending than the District, while Montgomery schools spend about the same.

Futrell said yesterday that despite the gains shown in the report, schools will need a 20 to 25 percent spending increase to pay for the education reforms, including tougher graduation requirements, that many states have enacted since the 1983 report by the U.S. Commission on Excellence in Education, which denounced a "rising tide of mediocrity" in American schools.

Futrell said she was "gloomy" about the financial condition of the nation's schools because of the prospect of federal budget cuts stemming from the Gramm-Rudman-Hollings act and declining energy and farm prices.

However, Education Secretary William J. Bennett disputed that assessment.

"There they go again," Bennett said in a statement. "Only the NEA could be gloomy in reporting that teachers' salaries have increased by 7.3 percent while the rate of inflation is only 3.2 percent. Most Americans will think this is good news . . . .

"Teachers' salaries are increasing, education reform is continuing, and the NEA should stop moaning, cheer up, and help out in the effort for better schools and teachers."

The NEA, which has been publishing its "estimates of school statistics" for several decades, uses data on budgets and enrollments provided by state education departments. It issues its report about one or two years before final figures -- usually quite close -- are released by the federal government.

The 7.3 percent increase in the average teacher salary for 1985-86 marks the fifth year in a row that salary raises nationwide exceeded inflation. But these gains followed four years in which teachers' purchasing power fell because raises lagged behind the increase in prices.

Depending on the inflation rate for the remainder of the school year, the NEA estimates that teachers' real gain in purchasing power will be from 3.5 to 3.7 percent, a rate almost reached last year and in 1982-83, but not seen previously since the low inflation years of the 1950s.

Since 1980-81 the real average salary of teachers, adjusted for inflation, has risen by 14.4 percent, the NEA said, after dropping by 11 percent over the previous five years. Even with the good performance recently, the purchasing power of the average teacher's salary is up slightly less than 2 percent over the decade.