If you'll dig a little deeper, you'll see it wasn't all legislation. From your full text link:
Although these educational failings resulted in part from funding constraints, Congress recognized that the problem reflected more than a lack of financial resources at the state and local levels. Two federal-court decisions, which the Senate Report characterized as "landmark," see id., at 6, demonstrated that many disabled children were excluded pursuant to state statutes or local rules and policies, typically without any consultation with, or even notice to, their parents. See Mills v. Board of Education of District of Columbia, 348 F. Supp. 866 (DC 1972); Pennsylvania Assn. for Retarded Children v. Pennsylvania, 334 F. Supp. 1257 (ED Pa. 1971), and 343 F. Supp. 279 (1972) (PARC). Indeed, by the time of the EHA's enactment, parents had brought legal challenges to similar exclusionary practices in 27 other states. See S. Rep., at 6.
If you'll read Mills and PARC, you'll see that those decisions relied on the equal protection and due process clauses of the Constitution. Both Reinquist and Congress thought those two cases were very important. Even if the statute is repealed, the equal protection and due process clauses will remain, and I'd predict a slew of new court cases on those bases.
Actually though, I didn't think you'd be interested in Honig so much for the rationale, but because you'd mentioned the problem of behavior-disordered students disrupting classes for the others.
Yes, the "Equal Protection" clause has been used a lot by the courts, just as the "Commerce Clause" has been used by Congress to imply that Congress can pass whatever legislation it wants to as long as it can make a hand-wave to the commerce clause
The position of the various courts these days, seems to be that no government funding of any activity is allowed unless every identifiable group benefits equally from it. Thus you may not fund libraries for people to read in, unless illiterate vagrants are allowed to also use the facility as an informal shelter. Thus you are not allowed to fund public schooling unless each identifiable group comes out with an equal level of educational attainment (which is the point of "No Child Left Behind").
In this legal climate, government funding (especially federal funding) of any activity comes with a huge mass of strings attached.
The only solution, once the system has been made sufficiently unworkable, is to abandon it entirely, as increasing numbers of middle-class parents are doing. Up until now, the upper-middle-class has been able to escape the social pathologies of the underclass by moving deeper and deeper into the suburbs. As soon as that approach becomes no longer workable, you will see increasing middle-class support for radical change