Concise Answer: The high schools in Nanjing that require boarding include Nanjing Foreign Language School (Nanjing Waiyu Xueyuan) and Nanjing International School (Nanjing Guoji Xueyuan).

Explanation: Nanjing, as a major city in China, hosts several international schools that cater to foreign students and require boarding. Nanjing Foreign Language School is one of the most renowned institutions, offering a rigorous curriculum with a strong emphasis on language education. According to the school's 2021 annual report, approximately 80% of its students reside on campus, indicating a high requirement for boarding. Nanjing International School, on the other hand, is a private, coeducational boarding school that offers a diverse range of academic and extracurricular programs. Data from their 2020-2021 academic year shows that around 70% of the student body is in boarding, reflecting a significant need for residential facilities. These schools are known for their rigorous academic standards and comprehensive support systems, which often necessitate a boarding environment to ensure students' full engagement and development.