Coalitions of unlikely allies can be powerful, especially in convincing legislators that a wide variety of constituents support a particular issue. Contact someone in the group that you are interested in networking with and ask if you can come to one of their meetings. Explain your common interest and suggest a possible joint activity. Colleges and universities are good places to gather resources and support. Work with faculty and student organizations to create an educational event.
Most schools have funds to pay for academic or prominent speakers.
School papers will also cover campus events or write articles about campus organizations. Some professors might be willing to creatively involve students in their classes in grassroots actions or be willing to open their class up to an outside speaker for a day. Remember when approaching a professor that schools are places for academic study, and only academic material will be allowed into a classroom. High school students are often very concerned about the world in which they live, but feel that they have no control over events. Many are involved in church and community groups.