He said new taxes and more cuts in service would be needed.
This means that cuts of $61 billion will be needed to meet the law's target.
But more cuts were needed, so the board voted to trim the professional staff by 4.7 percent.
The Republicans say that a cut is needed to spur economic growth.
But economists say further cuts will be needed before the economy changes direction.
He said the cuts were needed because of the increasing competition in the publishing industry.
"Your cuts are not needed to balance the budget or to cover all children," the letter said.
They say further cuts are needed in government before such steps would be appropriate.
Further cuts in government spending will be needed to give a promised new boost to industry.
No cuts in aid to local governments would be needed, he said.