HW学校官网上明确要求的成绩是 ISEE，但是也是test optional的，根据你的情况，大概率不需要托福。
学校因为没有 ESL 课程，因此，对语言要求非常高，这是官网信息，供参考：
Harvard-Westlake admits international students who move here with their parents and intend to complete their secondary education through the 12th grade in our academic program. Since we do not offer a program in English as a Second Language (ESL), students need to be completely fluent in English for reading, speaking, and writing. Harvard-Westlake is a day school and does not offer any boarding or homestay arrangements. Students need to move here with their family and live with their parents.