Ms Morgan ushered in new, tougher Sats exams this year, which led to some pupils being reduced to tears and sparked a significant backlash from teachers and parents over the difficulty of the tests.
Headteachers have already called for the test results not to be published amid fears that they will provide a skewed impression of primary school performance.
And in an attempt to manage expectations, Ms Morgan told the BBC that Tuesday’s Sats results should not be looked at against previous years.
"They simply cannot be compared directly," she said.
Individual schools will receive their tests results tomorrow, while the provisional national results will also be made public.
But Ms Morgan said that critics of the new primary curriculum will try to claim that lower results will mean the new system has failed.
“Nothing could be further from the truth. I don't know what the results will look like yet. But I have always been clear that politicians trumpeting ever-rising test results, at the expense of high standards is entirely wrong," she said.
The Cabinet member said lower results would not mean children had “performed any worse”, but rather that the bar had been raised.
"Neither schools nor parents should try to compare this year's results with previous years,” she said. “The tests are new and are based on a new, more rigorous national curriculum – based on the best evidence from across the world."