Parents of children who attend Bancroft Elementary School were warned yesterday by Principal Kenneth R. Milner that they should stress to their children "the importance of coming directly to school and remaining in the company of an adult at all times."

Yesterday's warning in a letter to the parents of 700 children followed the disclosure Tuesday that three 5-year-old girls have been sexually assaulted in or near the Northwest Washington school in the last three weeks and that police believe one man was responsible.

But, to scores of parents, Milner's warning was too little, too late.

Parents, many of whom now accompany their children to and from school because they said they are worried about the children's safety, said they were angered that they had not been told about the assaults earlier, the first of which occurred in a school restroom on Sept. 18.

"I'm not saying that Mr. Milner was wrong, but, in my opinion, he used bad judgment in withholding the information about the assaults," said Lenore Peters, whose two children, Ayanna, 7 and Kwadjo, 6, attend Bancroft.

She said she had talked to Milner after the first assault when her son mentioned something to her, Peters said. "When I asked [Milner] about the incident, he said everything was fine. He had a smile on his face. He should have shared his ideas with parents right away instead of trying to keep things hush-hush. We are a part of this school too and we must face problems together." Peters said she learned of the other incidents Tuesday night.

The first assault occurred about 2 p.m. Sept. 18 when a girl was accosted in a Bancroft stairwell by a man who took her to a restroom and fondled her sexually, according to police. On Tuesday of last week, another girl was walking alone in a school hallway about 2:15 when a man grabbed her and forced her to go with him in a wooded area behind the school where he fondled her and then took her back to the school, police said. The latest incident occurred about 6:30 p.m. Monday, when a girl playing near the school was approached by a man who took her to the same woods and forced her to submit to sodomy.

In addition, last June, a man struck and knocked to the ground a 9-year-old girl pupil who resisted his attempts to take her to the woods behind the school. Police said they suspect the same man in all four attacks becausee the girls gave similar descriptions of their assailant and of the circumstances of the assaults.

While Milner refused to discuss the matter with reporters, a school spokesman said that the Bancroft principal withheld the information because he was working in cooperation with D.C. police. Shelton Lee, spokesman for the school security and safety division, said "To paraphrase the superintendent [Floretta D. McKenzie], the principal was operating on a request of the police department to be somewhat quiet about the information in order to assist in a possible arrest. With hindsight, she would now feel that it would've been better to inform the parents."

However, police spokesman, Lt. William White III as well as officers close to the investigation said that Milner was advised to tell parents about the incidents so that children could be on guard.

White said, "First and foremost, it is our policy that when incidents of this nature occur we disseminate the information to the parents and community leaders as soon as possible so that they are aware of what's transpiring. This allows them to take various precautionary measures.

"We don't want to jeopardize a child's well-being by withholding information with a view towards making an arrest," White said.

D.C. Police Chief Maurice Turner said that widespread knowledge of the assaults would compromise secret undercover police operations at the school, but that he was not aware of a police order not to divulge details to parents.

Turner said undercover officers had been watching the school for about a week. "After the [second sexual assault], we planted someone there during school hours" in hopes of catching a suspect, Turner said. He said it was "unfortunate" that the third attack occurred outside the school on a nonschool day [Columbus Day] when no officers were on duty there.

Milner, told of the comments by police, refused to comment.

Meanwhile, police yesterday tightened security measures at the school and formed a task force to "vigorously pursue leads in the case," White said.

The task force is composed of officers from the police sex offense branch and the 4th District and investigators and aides from the school safety and security division, according to White.

Two security investigators and an aide have been assigned to Bancroft, Deputy Superintendent of Schools Andrew Jenkins said, adding that at least one investigator will remain at the school for the rest of the school year.

After school yesterday, Bancroft students were given copies of Milner's letter to take home to their parents. Several parents who arrived at the school about 3 p.m. to accompany their children home scoffed at the letter.

"The way I feel now, I could take my children out of this school," said Martine Portee, whose two sons, aged 9 and 5, attend Bancroft. "As late as last week there were few security precautions taken at the school. The doors remained unlocked after classes were in session. Anyone could walk in. This letter states that they're going to start locking doors. Of course they will now. But it's too late. . . . If they had just sent a note earlier."