Cusco  has more Spanish schools than any other city in Peru, though it is hard to be truly immersed in Spanish unless you can somehow isolate yourself from English speakers. Considering what they include, the school packages are considerably cheap: pre-arranged hostel or homestay with local family, breakfast, airline reservations, volunteer work options, city tour, dance and cooking classes, lectures and movies.
An intensive group class with all these perks runs around US$200–300 per week with 20 hours of classes, while a private package is around US$300–400.
A private teacher, without lodging or food, is US$9–11 per hour. All prices quoted are for a week with 20 hours of classes.
Academia Latinoamericana de Español (Plaza Limacpampa Grande 565, tel. 084/24-3364, www.latinoschools.com , US$190 private classes, US$160 group classes) is a professional, family-run business with schools in Peru, Ecuador, and Bolivia. They have great host families in Cusco and offer volunteer programs and also university credits through New Mexico State University.
Amigos Spanish School (Zaguan del Cielo B-23, tel. 084/24-2292, www.spanishcusco.com , US$120 group) gives half of its income to children with disabilities and has highly recommended teachers.
Centro Tinku (Nueva Baja 560, tel. 084/24-9737, www.centrotinku.com , US$180 group, US$220 private) is a cultural institution that offers standard and custom-made Spanish and Quechua classes. All the teachers are fully certified.
Off the Plazoleta San Blas  is the affordable and quaint yet professional Mundo Antiguo Spanish School (Tandapata 649, tel. 084/22-5974, www.learnspanishinperu.net , US$55 group, US$190 private), run by a friendly Peruvian-Dutch couple. The main aim of this school is to keep it intimate, personal, and welcoming.
Maximo Nivel (El Sol 612, tel. 084/25-7200, www.maximonivel.com , US$110 group, US$200 private) has schools all over North and South America.