Because, according to the article "the legislation would 'lead to severe cuts in Medicare and Social Security' and impose unrealistic limits on education spending. (emphasis added)
The federal government is out of money. And $14,290,000,000,000 in debt. Which isn't enough debt, which is why we are having this discussion to begin with. So under the circumstances, there really should be no such thing as an unrealistic spending limit on anything. Much less education, which is a) the responsibility of the states and local governments if it is the concern of the state at all, and b) not the responsibility of nor an authority granted to the federal government.
And it shows how far we've come when the problem is that the president is concerned about spending too little.