An analysis of their pupils' scripts did not convince an independent team of specialist markers that the leak had not boosted performance in comprehension tests for 11-year-olds.
However, the rest of the borough's 60 primary schools were given the all-clear after an investigation of pupils' scripts proved they had not been coached to answer the test.
Wandsworth council was leaked details of this year's key stage 2 English test by an official from the Government's own test body, the Qualifications and Curriculum Authority. He told a former colleague, by then a senior officer at Wandsworth Council, that the test would be on the theme of spiders and would include a comprehension exercise based on a poem. She told two junior colleagues in her team who then began systematically briefing schools about what would be in the test.
A QCA spokesman said: "In the vast majority of cases, the markers have found no evidence to suggest that pupils had prior knowledge of the content of the tests or that they had been coached to give particular answers. In four schools investigations are continuing into some children's scripts."
The QCA official was given a final written warning and transferred from the authority's test team to a different post within the organisation after an internal inquiry found that he was responsible for the leak. The three Wandsworth officers were given final written warnings and the senior official was demoted.