Successive governments have loaded so much work onto heads, they find it difficult to share responsibility with senior colleagues, who are treated as "mere underlings".
The Cardiff University authors found that while schools embrace the idea of senior management teams sharing responsibility, pressure from Whitehall is having the opposite effect.
Faced with a whirlwind of change since 1988, heads have been retreating into a more "hierarchical" model of management.
While they might be tempted to give freedom to staff to express ideas or to operate as equals, pressure from the Office for Standards in Education and the Government means they are more inclined to play safe, says Mike Wallace, professor of education management at Cardiff.
"Senior staff find themselves becoming mere underlings doing their master's bidding," he said. "If you have strong accountability, then heads are going to play things close to their chest."
The findings are published in Senior Management Teams in Primary Schools: the Quest for Synergy by Routledge this week.
It includes four case studies showing how heads tried to run their schools more democratically despite government reforms. "The best solution was the head who operated most equally," says Professor Wallace. "The senior staff accepted her authority but understood that occasionally she would pull rank."