In February, Croydon's head of education asked the Harris Federation, a powerful academy chain with 38 schools across London, including nine in Croydon, to explain why many of its pupils 'disappear' before their exam year.
Paul Greenhalgh's concern was based on an investigation by the Guardian, which found a sharp drop in pupil numbers before GCSEs in 2012 compared to the number enrolled in the same group the previous year. Harris Academy South Norwood was mentioned specifically in the article because pupil numbers had fallen 20 per cent during that period.
There was no evidence to suggest lower-achieving children had been deliberately removed and educated elsewhere, the article said, but there were questions which needed to be answered.
The council seemed to agree. Mr Greenhalgh, director of children, families and learning, said figures for one of the academy chains mentioned in the article had been analysed and he was concerned.
"We have written to that chain to seek an explanation and to secure an answer in terms of the express concerns we have from what we can see in the data," he told a council scrutiny meeting.
Though no one at the council would confirm it at the time, the chain in question was the Harris Federation. Questions were also asked about Oasis Community Learning, another major academy provider in Croydon that featured on the Guardian list.
The authority wrote to the Education Funding Agency (EFA), which manages funding for academies and free schools, to seek an explanation about where the pupils had gone.
Sean Fitzsimons, the Labour councillor who first raised the article with the council, said he was reassured that an investigation would take place, but stressed the need for transparency.
As a result of the letter, the Harris Federation met with Mr Greenhalgh and other council officers in May.
Since then the concern about 'disappearing' pupils appears to have, well, disappeared. As if reading from the same crib sheet, the Harris Federation and the council issued a statement this week saying they had agreed to be better at sharing information with each other.
A Harris spokeswoman said:
"The Federation met with Croydon after the EFA looked into the issue and found that the level of pupil turnover was consistent with the local authority as a whole. The meeting with Croydon was useful and we agreed with them the ways in which we would share data with each other."
A council spokesman said:
"The council has had a very constructive meeting with the Harris Federation and have agreed all essential information that will be shared in the future, to ensure data sharing systems are consistent and clear.
"Good communication has been established between the Federation and the council, which will allow both organisations to fulfil their duties and ensure the needs of all young people are met."
Earlier in the week, however, a council source had told the Advertiser that the Department for Education (DfE) had warned Harris to "stop their current practice and not exclude these children".
A DfE spokeswoman said this week that the matter had been resolved without its intervention.
It is possible, of course, that there was nothing untoward about the variation in pupil numbers during the years in question, and that the council's initial concerns were a result of not having access to pupil movement data for academies.
But, recall Cllr Fitzsimons' warning at the time the issue first came to light.
"I get the impression," he said, "that the council would not want any problems with its academy providers to be out in the open, but this is a serious issue which warrants further explanation."
Next week the Harris Federation will open two more schools in Croydon, and it will probably be relied on even more heavily in the coming years as the council tries to meet unprecedented demand for places.
In that light, perhaps it is unsurprising that questions about disappearing pupils have vanished.
