ANNAPOLIS, FEB. 23 -- Maryland School Superintendent David W. Hornbeck said today he will step down in June from the state's top education job that he has held for 12 years to pursue "new and different challenges."

A gentle man with passionate beliefs about the state's need to help disadvantaged children, Hornbeck made his surprise announcement to the State Board of Education, forsaking its offer of another four-year term.

"When the board and I did the quadrennial analysis of whether we would remarry," the 46-year-old school chief said in an interview, "I simply came to a different conclusion. There is no single factor that has led to the conclusion. It's been 12 years -- a long time. I simply want to try my hand at something else."

Hornbeck said he had not decided on a new job, but was pursuing several possibilities "related to education" that would enable him to concentrate on what he called his principal interests: Helping students at risk of dropping out of school and enlisting youngsters in community service.

Hired in 1976, Hornbeck has had an unusually long tenure in the kind of position where, nationally, turnover is high. Only a few of his counterparts in other states have held their jobs longer.

During his reign, Maryland began Project Basic, a series of state competency tests that high school students must pass before graduation. A few of the tests, including the one in writing, had rocky beginnings, as educators around the state challenged their validity and squirmed in the glare of initial high failure rates.

Today Hornbeck called the project, which couples the tests with additional financial help in school systems where many students fail, "a very fundamental initiative" that has "penetrated kindergarten through 12th grade," increasing the quality of instruction.

Some other initiatives sought by Hornbeck have been less favorably received. He was unsuccessful, for instance, in persuading the state school board to require all high school students to perform volunteer work in their communities.

And he said today he remained dissatisfied with the way Maryland allots education subsidies to its 24 school systems. Despite repeated recent increases in education aid and changes in the formula for doling out money, he said the state's distribution method remains "unjust and unfair," resulting in the lowest school budgets in Maryland's poor rural counties and in Baltimore, which have the greatest proportion of difficult-to-educate youngsters.

He said he remained disappointed, too, with disparities in teacher salaries and with the fact that only about 200 of the state's elementary schools offer prekindergarten classes, which have been shown to benefit children from poor families.

Last night, Laslo V. Boyd, the education aide to Gov. William Donald Schaefer, said "there was no sense of any dissatisfaction with David," noting the State Board of Education's offer of contract renewal and that Schaefer had asked the legislature to raise Hornbeck's salary from $72,700 to $101,300.

A native of Knoxville, Tenn., Hornbeck earned theology degrees from Oxford University and Union Theological Seminary in New York. He holds a law degree from the University of Pennsylvania Law School and was the executive deputy secretary of education in Pennsylvania before being hired by Maryland.