Montgomery County police yesterday continued their cradkdown against drug use in county schools, arresting 17 young people near four different schools - two 12-year-olds among them.

Yesterday's arrests brings to 250 the total number of young people arrested since the cracdown began six weeks ago. Almost all of those arrested have been charged with drug-related offenses.

The latest series of arrests began yesterday at 8 a.m. when six students aged 12 to 14 were arrested adjacent to the campus of Eastern Junior High School in Silver Spring and charged with possession of marijuana and alcohol.

Two hours later, three students, all 17, were arrested for possession of marijuana on the school grounds at Wheaton High School. At 11 a.m. police arrested three students whose ages ranged from 12 to 16 for possession of marijuana off the grounds of Argyle Junior High in Wheaton. The 12-year-old was an Argyle student, the 14-year-old attends a private parochial school and the 16-year-old is a student at Kennedy High School, police said.

Five more students, aged 14 to 15, were arrested at 12:30 p.m. off the grounds of Winston Churchill High School in Potomac. All were charged with marijuana possession.

Late Tuesday, police also arrested four youths, ages 15 to 17,near the campus of Gateway High School in Rockville for possession of marijuana and PCP. Two of the students attended Richard Montgomery in Rockville, police said.