The best language school in Huaraz [1] is Sierra Verde (Lucar y Torres 538, tel. 043/42-1203, sierraverde_sp [at] hotmail [dot] com), which offers both private classes and group lessons.
Another good option is Langway (Luzuriaga 975, #203, tel. 043/42-4286, langwayhz [at] yahoo [dot] com), which offers classes not only in Spanish, but also English, Italian, German, Japanese, and Quechua.
The best volunteering option in the Cordillera Blanca is undoubtedly The Center for Social Well Being (tel. 01/252-2947, www.socialwellbeing.org [2]). The goal of this nonprofit organization, founded in 2000 by veteran anthropologist Patricia Hammer, is to improve the lives of Andean people.
The organization is run through the delightful Casa de Pocha, a five-hectare highland ranch outside of Carhuaz, and offers many opportunities for both volunteering and academic field trips. The center also offers Quechua and Spanish language lessons, and health and healing workshops.
Links:
[1] http://www.moon.com/destinations/peru/huaraz-and-the-cordillera-blanca/huaraz
[2] http://www.socialwellbeing.org