This study investigates the relationship between age at immigration and educational achievement at age 14 among all the students (about 45,000) who immigrated to Israel between 1952 and 1970. The relationship is examined for verbal and nonverbal components of an achievement test, in subpopulations defined by gender and ethnic background (Western-versus Eastern-born children). The findings indicate a monotonic decrease in achievement as a function of immigration age starting at the age of 7. This decrease is considerably stronger for the Verbal subtest than for the Mathematical subtest, particularly in the Western group. These results refute the vulnerable age hypothesis: They support the view that the foreign language acquisition factor plays a central role in the relationship between age of immigration and scholastic achievement, and are consistent with the expectation of a monotonic decline in achievement as age of immigration increases (and length of residence decreases). Hence, when immigration involves the need to learn a new language, the drop in school achievement is likely to be particularly marked in subject areas requiring higher levels of mastery of the language of instruction. Finally, the results suggest that age 7 may represent a critical age for the scholastic achievement of immigrant students.