National Diffusion Network Act - Directs the Secretary of Education to carry out a program to promote the use of exemplary educational programs, products, and practices to interested elementary and secondary schools. Requires the Secretary to provide information, materials, training, technical assistance, and evaluations. Authorizes the Secretary to make grants to, and contracts with, public and nonprofit private educational institutions and organizations to carry out such program. Declares that such program shall be deemed to be a continuation of the National Diffusion Network for which provision is made under the Education Consolidation and Improvement Act of 1981. Directs the Secretary to allocate funds available under such Act to such program. Authorizes additional appropriations, if necessary, to carry out such program in FY 1986 through 1989.