To engage with local, state or even the federal government on STEM education you will need to get a solid foundation on education policy at that level. Your local school board sets much of the curriculum for local schools. Engage with them to learn what they think matters in your community.
Local school systems have to meet state standards with respect to mathematics and science. The Indiana Department of Education website has the current standards listed for mathematics and science. These standards indicate what students should know at each grade level, but not how the subjects will be taught or what books and materials will be used. Local school districts decide these. So if you want to get involved in curriculum and materials, engage local. If you care about standards and assessments, these are state-level issues generally.
The federal government, through the Department of Education, sets policy for student achievement by attaching requirements to federal education grants. In the past, programs such as No Child Left behind and Race to the Top have been used to foster education reform by attaching it to federal grants. To engage the federal government on STEM education, start with your local representative's office or your state senator's office.