The money, equivalent to 25p extra per meal, has subsidised other school costs, says the Local Authority Caterers Association.
The study is the largest ever on the school meals market, now worth almost pound;1 billion a year, with an average of just under 3 million meals served a day.
Sales in primary schools in England and Wales have risen by more than 18 per cent since 1996, but dropped by 8 per cent in secondaries. Overall sales have increased by 10 per cent.
LACA says savings from better marketing, cost control and competition would allow an extra 5,500 teachers a year to be employed.
Neil Porter, the association's vice-chair, said the loss of pound;154m was preventing caterers from buying local and organic produce.
"It would also allow us to offer children more roast dinners instead of pre-prepared meals such as shepherd's pie," he said.