Two private preparatory schools have given just six weeks' notice that they will close, fuelling fears that the independent sector is already being hit hard by the financial crisis.
Bramcote Lorne Prep in Retford, Nottinghamshire, and Brigg Prep in Hull will shut at the end of this term after failing to attract enough pupils to remain open.
Both are members of the United Church Schools Trust (UCST), a chain of independent schools and the sister charity of the United Learning Trust, the country's biggest academy sponsor.
The prep schools will merge with other UCST schools, with staff and pupils able to transfer. But not all teachers' jobs are guaranteed beyond the end of the academic year.
David Hanson, the chief executive of the Independent Association of Prep Schools (IAPS), said more mergers and closures would follow.
"Now is the time for schools to plan, before the worst of the recession affects them," he said. "If they wait until it's too late, mergers become like shotgun weddings.
"The recession will not necessarily be terrible for the sector. Schools will have to make sure they are offering value for money and will come out of a recession stronger."
Mr Hanson said that the IAPS would be distributing step-by-step advice on mergers to its schools next month. Some schools are so keen for the information that they have asked for advance copies.
Noble Hanlon, an accountant at Haysmacintyre, told the third annual Wellington-Marlborough preparatory heads conference this week that more closures and mergers were likely.
"Prep schools will not be immune from the recession and action will need to be taken to protect income and control expenditure," he said.
The two UCST schools that they will close have failed to turn around declining pupil numbers. A third prep, Rathvilly School in Birmingham, announced last month that it was closing its doors after it, too, suffered a slump in pupil numbers.
Bramcote Lorne Prep, which has 86 day pupils and six boarders, will merge with Lincoln Minster School, and Brigg Prep, which has 74 pupils, will merge with Hull Collegiate School from January 1.
The UCST took over Bramcote Lorne Prep and Brigg Prep in 2005 and 2004 respectively.
Sir Ewan Harper, chief executive of the trust, said: "At the time both were facing falling rolls. Despite the best efforts of everyone involved and the proud tradition that both have as schools, we have been unable to reverse this trend.
"Our experience of mergers in the past is that they are more successful when they happen decisively and before the schools are allowed to enter periods of uncertainty and drift.
"This consolidation of two of our smaller schools with larger all-through schools is a pre-emptive move. Had either of them been stand-alone independent schools, their prospects for the future would have been grave."
Parents have reacted angrily that they were given such little notice of the closures.
A delegation of parents from Bramcote Lorne Prep approached Cognita, the chain of private schools headed by Chris Woodhead, the former chief inspector of schools, to see if it would be interested in taking the school over. But Cognita, a for-profit company, turned the prospect down because the school is too small.
Bramcote Lorne Prep parents have also criticised the merger plans because Lincoln is more than 20 miles away.
In the summer, Wentworth College in Bournemouth was rescued from closure by the UCST after it went into administration following a decline in pupil numbers. The school has now been linked with Hampshire Collegiate School in Romsey, with its principal becoming executive principal of Wentworth College, and now going through a restructuring process that could lead to redundancies or teachers' hours being cut.