A district judge acquitted a teen of hurling a classroom table from the third storey of a secondary school block, finding doubts in the claims of two other students who pointed to him.

District Judge Eugene Tay in the Youth Court noted that the two witnesses who said the boy was the culprit were both inside a classroom in the opposite block some 30m away, and it was raining heavily then as well.

"I was not convinced that the line of sight of the (two witnesses) was totally clear or unobstructed," he said in judgment grounds last month.

"This, coupled with the fact that the incident would have taken place in a matter of seconds and that the person who had thrown the table would have been moving instead of being static, I concluded that (they) would not have seen the culprit for more than a few seconds," he explained, adding that he accepted the submission of the defence on this aspect.

The then 15-year-old boy was charged with committing a rash act to endanger the personal safety of others.

The incident happened at a school in Jurong on May 22 last year at about 11am.

Deputy Public Prosecutor Derek Ee had argued that both witnesses were 100 per cent sure of the identity of the culprit.

He said that even though there was bad blood between them, and they had motive to frame the youth, they had withstood cross-examination and stood firm on their evidence.

They had nothing to gain by framing the youth and were credible witnesses, as were the other four witnesses, including a teacher.

But defence lawyer Hannah Tjoa countered that of the six prosecution witnesses, only two were direct eye-witnesses, and they had discussed the evidence between them and confirmed each other's version, "thus implanting false memories in both of their minds".

District Judge Tay noted that the two direct eye-witnesses were unable to recall what the teen was wearing then, which weakened the strength of their testimony.

He also found that the evidence of the other witnesses did not help prove the case beyond reasonable doubt. The identities of the parties involved were redacted.

The prosecution has dropped its appeal.

Correction note: This story has been updated for clarity.