A former Ofsted chief inspector has warned Education Secretary Michael Gove not "to believe his own hype".
Writing for website The Conversation, Sir David Bell said Mr Gove should not surround himself with "yes men".
Mr Gove became embroiled in a row after deciding to replace the chair of Ofsted, Labour's Baroness Sally Morgan.
He says he wants to "refresh" the leadership of the schools' watchdog and denies his intention to remove the Labour peer was politically motivated.
In a speech in east London on Monday, Mr Gove is expected to set out his own ambitions for state schools, saying they should be more like independent schools.
He will call for more testing, in particular encouraging state schools to adopt the common entrance exam - an exam sat by some private school pupils.
Mr Gove will also back plans for individual secondary schools to be able to take the OECD's international Pisa tests.
State schools will be able to stay open longer and the education secretary will repeat calls for tougher discipline.
Mr Gove will also say that he wants private and state schools to become indistinguishable.
"For decades, the dominant consensus has been that state education in England was barely satisfactory," Mr Gove will say, but that such a "pessimistic view is no longer tenable" as state schools have improved.
But the row over the change at the top of England's schools watchdog has intensified further with the intervention of Sir David, who as well as having served as Ofsted's chief inspector later worked alongside Mr Gove as his most senior civil servant at the Department for Education.
In the article for The Conversation academic website, Sir David warns the education secretary of the risk of becoming isolated by listening only to supporters.
"The day-to-day grind of policy battles, firefighting and political ding-dong can start to cut you off from outside ideas and thinking.
"The row over Ofsted's leadership shows the importance of retaining and being seen to retain independent voices near the top - not simply 'yes men'," writes Sir David, who is now the vice chancellor of the University of Reading.
Sir David said Mr Gove should not dismiss all critics of his education policy but should engage with those offering an "intelligent critique".
On Sunday, Mr Gove said he had appointed Baroness Morgan, and despite the fact he felt she had done a "fantastic job" the position needed a "fresh perspective".
Baroness Morgan, who has not had her term in office renewed, told the BBC she was the victim of a "determined effort from Number 10" to appoint more Tories.
The decision has been criticised by the Liberal Democrats and by Labour's shadow education secretary, Tristram Hunt, who said the "disappointing" move was politically motivated.
The director of the Institute for Government, Peter Riddell, said the decision not to reappoint Baroness Morgan had "raised some eyebrows" but there was nothing new about ministerial involvement.
Another former Ofsted chairwoman, Zenna Atkins, has backed Mr Gove over Baroness Morgan's departure, saying she has "seen nothing that suggest it's a political move".
Sir David also had tough words about teachers' unions, saying their "political naivety has been astonishing".
"Their barrage of industrial action and knee-jerk opposition to any change has allowed the education secretary and his supporters to characterise them as cartoon-like bogeymen," he writes.
Sir David was part of a group of business leaders and academics who published a report last week calling for a more independent, non-political approach to education policy.
The row over Baroness Morgan comes a week after the chief inspector of schools in England, Sir Michael Wilshaw, accused staff at the Department for Education of briefing against his organisation.
Sir Michael Wilshaw had said he was "spitting blood" after the Times reported two right-leaning think tanks were to criticise Ofsted.
Mr Gove denied claims his team briefed against the inspectorate which in turn was welcomed by Sir Michael who said he would defend his team against "unfair criticism".