Military enlistments by high school graduates and blacks increased but the number of women volunteers declined slightly in the April-June period, the Pentagon reported.

Defense officials were particularly pleased with the rise in high school graduates because they are viewed as a key measure of improving quality of the all-volunteer military force.

Officials said they hope for even better results in the current July-September quarter because this is traditionally the best recruiting time of the year, following high school graduations.

The number of young blacks volunterring total 17,000 up 2,900. Blacks represented 23 percent of all service enlistments, compared with 20 percent in the January-March period.

Pentagon officials said the persistent high rate of civilian unemployment among young blacks is a major contributing factor in their growing enlistments in the armed forces.

The number of women enlisting in the April-June period totaled 9,500, dropping by about 700 frin January-March. Women appear to lean more toward the Air Force than the other services. Twenty percent of the air Force's volunteers in the most recent quarter were women, compared with 14 percent for the Army, 8 percent for the Navy and 6 percent for the Marines.