The Pupil Achievement Tracker computer system, supplied to all schools by the Government last term, allows heads to see whether a teacher's classes are performing as expected. Teaching unions had feared the system might lead to the dismissal of staff whose pupils under-performed.
But Mr Miliband told a conference of education advisers and teachers in London this week that he had "no ulterior motive".
"This is about more pupils fulfilling their potential through good teaching," he said.
"Heads already have a range of interventions that arm them to engage with quality of teaching. I've no directives up my sleeve."
Mr Miliband's comments came at a conference organised by the Education Network.
It marked the launch of School improvement: making data work a booklet by John Fowler and Simon Bird, exploring how councils use information.
The study found that education authorities were improving their use of data in education but were keeping governors in the dark.
The researchers found that 40 per cent of LEAs did not share school monitoring reports with governors.
They said the situation was "a cause for concern", because many authorities had already been criticised by inspectors once for failing to providing the crucial reports.
The fact that governors were uninformed would also damage the performance of schools in inspections, they added.
Joan Sallis 29
School improvement: making data work is available from www.ten.info