Summer vacation has been extended by one-half day for public school students in Prince George's County. The board of education, at a recent meeting, accepted a recommendation from the superintendent of schools to drop the half day of classes that had been scheduled for June 17th.

The half-day for June 16th, however, stays in the school calendar. Superintendent Edward J. Feeney told board members the rearrangement would still leave the system with 182 days of classes this school year - two above the Maryland minimum. Cutting out the half-day of classes on June 17th will allow teachers, whose last day is June 17th, a full day to clean and pack up for the summer, he said.

Seniors in Prince George's County high schools are finishing even earlier. Their last day is June 3rd, with graduation ceremonies to be held between June 3 and 15th.

For some students, however, the vacation will be short. Summer school begins June 27th.

Three historic sties in Maryland have been recommended for inclusion in the National Register of Historic Places. The Old Salem Church and Cemetery in Catonsville; Bon Air, near Fallston; and Belair, Bowie and Belinda Springs Farm in Sharpsburg have been nominated. If they are added to the register, they would become eligible for restoration funds from the National Park Service.