Phoenix Zoo
One of the country's largest nonprofit zoos, with 3,000-plus animals across desert, tropics, and Africa trails in Papago Park. Homeschool co-ops of 15 book the school field-trip rate of $8 a student (one free adult per 10), and the zoo runs dedicated seasonal Homeschool Days ($20, or $10 for members) — both well under the roughly $35 gate.