When Morrisons, the brash yellow-and-black branded family supermarket chain, merged with Safeway in 2004, the stock market was initially ecstatic. The share price soared to pound;2.50.
But a culture clash emerged between Morrisons' management in Bradford, and Safeway's west London leadership, and within a year the share price had dropped to pound;1.55.
"It has been a rocky road, a huge stream of bad news with six profit warnings. That is almost unheard of," said Jonathan Pritchard, an analyst with Oriel Securities.
"Safeway was patronised and treated as a mischievous child who needed to be controlled. All the top Morrisons guys went over to run Safeway, and then Morrisons started to fall. It was almost as it they were writing a manual on how not to do a merger."
But further north in Tyne and Wear, the newly-merged Jarrow school had already written that manual. When dwindling pupil numbers forced the amalgamation of the Springfield and Hedworthfield comprehensives in 2003, the parents were furious.
This was exacerbated when the results began rolling back in: only 31 per cent of Springfield and Hedworthfield pupils had been getting five good GCSEs in the previous years, on average. At the new 950-pupil Jarrow school, the figures dropped to a disastrous 24 per cent average over its first three years.
Les Jones, Jarrow's fourth head teacher in three years, said the enormous changes in a merger meant it was unlikely to ever go smoothly.
He said the difference between school and corporate mergers were that schools had a very different group of stakeholders, in the children, and their mergers were likely to be more poorly resourced.
"The initial process of amalgamation was not a success here, nobody denies this," he said. "I am told that behaviour was poor. The two communities were not initially at ease with each other. The school student and staff cultures were different. Parental support waned as attainment dipped."
He believed the school was now turning the corner, with a "sharp" governing body, improved student behaviour and 39 per cent of pupils getting five good GCSEs this year.
But he said education authorities should view the Hay Group findings very seriously, saying more resources were needed to address the dips in standards in many of the new schools.