To be sure there are 'little Ceasers' everywhere, even on mudcat, and a little power can easily be abused.

I sympathaize Donuel it's very difficult to refute allegations when you are in the dark.

Did these allegations come from a teacher's observations initially or were they reported anonymously to the school from some other source?
Who was the person responsible for the 'interrogation' and the insistance on 'secrecy' - as mentioned it can be easy to plant the 'preferred' answer to a young child eager to get out of an unpleasant situation.

As you point out, if a school does not pass on its 'suspicions' then they are not acting in the best welfare of the child; however, the social worker seems to have also been negligent in the time taken to follow up any allegations (from whatever source malicious, mistaken or otherwise) however flimsy she/he may feel they are.

I really think you need to discuss this with someone with expertise in this area.