About half a million fewer students will enroll in the nation's schools this fall, but annual education costs will rise by about $11 billion, the Department of Health, Education and Welfare projects.

An estimated 59.8 million people from kindergarten to graduate school, will enroll in public and private schools. This is about a 1 percent decrease from the 1977 total of 60.3 million. It represents the third annual decrease from a 1975 record of 61.3 million.

Enrollment is not decreasing at all levels, however. While kindergarten to eighth grade will drop by about 600,000 and high school by 200,000, colleges will gain an estimated 300,000 students, according to HEW's National Center for Education Statistics.

"Persons born in the mid-1950s to early 1960s [a period of high birth rates] are going on in their education" resulting in enrollment gains at higher education levels, explained the center's education statistics specialist, Vance Grant.

He said the $11 billion spending increase, from $144 billion currently to $155 billion for 1978-79, is mainly the result of inflation. Education costs are, therefore, "holding about level in terms of the dollar's purchasing power, he said.

State governments pay the largest part of the education tab, about 37 percent, or $57 billion in 1978-79. Localities are second in school spending, at more than $43 billion, or nearly 28 percent, while the federal government contributes another $16 billion, about 10 percent. The remaining one quarter, approximately $38 billion, comes from endowments, gifts, tuition and student fees.

The center noted in its back-to-school" forcast that three out of every 10 Americans will be involved in education either as students or teachers, or in a administration and support jobs. Salaries represent the biggest item in the education budget, Grant said.

Following the pattern of student enrollment, there will be about 20,000 fewer teachers in elementary and secondary school classrooms this year, and about 10,000 more teachers in colleges and universities.

Nearly one-third of the nation's college will be in school this fall, about 94 percent of the high school age group, and 99 percent of elementary schoolers.Ninety-two percent of five-year olds are expected to attend kindergarten; the absence of public kindergartens in may rural areas accounts for the other 8, Grant said.