Westcliff Primary Academy in Bispham had its SATs results investigated by the Government.
Officials from the Standards and Testing Agency (STA), which is responsible for overseeing the exams primary school youngsters take, said it launched a probe into "the administration of the key stage two national curriculum tests".
The school and its teachers were cleared of any wrongdoing, with the STA concluding "the integrity of the test results remained secure".
Headteacher Amanda Stokes is now back in charge after Pam Birch, a senior figure at the Fylde Coast Academy Trust (FCAT), which runs the school, temporarily took the reins.
The trust told The Gazette in September that "two members of staff" were "not in school" due to "unforeseen circumstances" - and insisted that parents were kept informed.
Two months later, it refused a Freedom of Information request asking for documents relating to the probe, citing an exemption relating to personal information.
The STA also refused to release files linked to the investigation, saying a minister had decided its disclosure could "prejudice the effective conduct of public affairs".
It did confirm this morning, however, that the probe lasted nearly four months, opening on July 19 and closing on November 4 last year.
One parent said they got a letter from the school saying two members of staff would "not be back for a while", but said they were not told about any investigation, and were also only told of "unforeseen circumstances".
While the headteacher has returned, the parent said the other member of staff has not. There is no suggestion of wrongdoing.
The parent also praised Pam Birch, who took Hambleton Primary Academy from having 'serious weaknesses' to being 'outstanding', saying she "sorted things out" during her stint in charge at Westcliff.
Standardised assessment tests – better known by their acronym SATs – are taken by children in key stage one and key stage two.
During key stage two, pupils sit six exams – one grammar and punctuation paper, one spelling test, two reading tests, and two maths papers.
Westcliff, in Crawford Avenue, recorded average scores for reading, well above average for writing, and average for maths, the latest Government league tables revealed.
Eighty-four per cent of pupils met the expected standard in reading, writing, and maths in 2019, the statistics showed, above 76 per cent in 2018 and 71 per cent in 2017.
Nobody at FCAT could be immediately reached for a comment.