An eighth-grade student with two or more other students pulled off the computer caper in which terminals at an East Side Manhattan private school allegedly were used to penetrate Canadian computer systems, according to well-informed sources.

An FBI investigation into the incident is continuing, and possible charges of wire fraud, stemming from the use of telephone lines in the incident, could result, but the age of the suspects has raised sensitive questions.

From April 16 to April 24, telephone lines of the Dalton School were used for 42 calls to the Telenet system, a common carrier of data communications operated by GTE Telenet Communications Corp. of Vienna, Va., according to an FBI affidavit filed in District Court here.

Officials of the Dalton school have little to say about the incident. Kleon Andreadis, an assistant to the principal, said: "It's an FBI investigation, not a school one." He repeated the same sentence when asked if there was a school investigation.

Dalton, an expensive coed school with about 1,200 students, is complying with the FBI investigation, Andreadis said.

No charges have been filed, and officials have not determined how much malice and how much mischief went into the planning of the illegal penetration of computer systems belonging to at least 21 Canadian companies and Universities.

The FBI obtained a search warrant for the school, and agents seized two plastic bags of computer printouts and a terminal log sheet when they carried out their search April 25.

Dalton principal Gardner Dunnan reportedly accompanied the FBI agents into the fifth floor computer room. The search was conducted in a gentle manner, according to reliable sources.

The extent of confusion or loss caused by the calls originating at the school is not known, but in one company, an unauthorized caller erased about a fifth of the computer. The loss was minimal, since that company was aware of the unauthorized entry into its system and had a back up that was able to restore the erasures in about 15 minutes.