His comments came as MPs raised concerns about possible grade inflation or “grade suppression” this summer after teachers have been given the responsibility to decide what grades pupils will receive.
Mr Lebus urged parents to give teachers the space to decide pupils’ A-level and GCSE grades so they do not feel “uncomfortable” as he insisted that teacher judgment was “pretty reliable”.
He said: “We’ve created a system which I think there are good incentives to allow teacher judgment to flourish and we’ve all got to play our part to support that.
Mr Lebus added: “I also think it’s very important that parents give teachers the space to do it because it’s always a worry that parents get terribly involved and teachers feel uncomfortable and there’s an intrusive interest so I think that’s a really important point and I wholly agree with it.”
Schools minister Nick Gibb said “parents can be reassured” that this year’s approach to grading is the “best alternative to exams that can be devised”.
But he said there were no plans to get rid of exams on a permanent basis.
Mr Gibb said: “In terms of the long term, we want exams back because they are fairer.
Tory MP Robert Halfon, chair of the education select committee, questioned whether grade inflation would last for years and whether an “all must have prizes” approach to grades had been adopted.
In response, Mr Gibb said: “No. This is a system where we trust the professionalism of teachers. They are the people who know their children well.”
Exam boards will carry out random sample checks of students’ grades this summer as part of the quality assurance process.
Jonathan Gullis, Conservative MP for Stoke-on-Trent North, raised concerns that pupils in some areas of the country, including his constituency, who do not benefit from having “sharp-elbowed parents” could become “victims of grade suppression” as schools may seek to avoid investigation over their grades.
But Mr Lebus said: “I think the idea that there will be any systematic pressure on teachers to underestimate student performance because they were worried about the school being subject to aggressive scrutiny, I don’t think it’s going to work like that, that’s not the intention.”