A committee of the Vermont House has approved changes in the state school funding system designed to curb growth in spending. The House Ways and Means Committee has been trying to slow spending growth that has forced it to recommend increasing the statewide education property tax three years in a row. Efforts to slow spending growth in light of declining student enrollments have not been very successful. Last month, local voters raised school budgets an average of 5.5 percent. The committee’s proposal, which now goes to the Appropriations Committee, would increase taxes in higher spending towns.