This study aims to explore the missing link between English textbooks used in high schools (9th-12th grades) and English university entrance exams (2010-2019) in Turkey on lexical and syntactic complexity levels by using corpus linguistics tools: AntWordProfiler, TAALED, and the L2 Syntactic Complexity Analyzer (L2SCA). Official textbooks and complementary materials obtained from the Ministry of National Education have been compared against the official university entrance exams from the past decade. The results show that: (i) differences in lexical sophistication level can be observed between the two corpora, the lexical sophistication level of the exam corpus was higher than that of the textbook corpus, (ii) there is a statistically significant difference between the two corpora in terms of lexical diversity, the exam corpus has a significantly higher level of lexical diversity than the textbook corpus, (iii) statistically significant differences also existed between the two corpora regarding the syntactic complexity indices. The syntactic complexity level of the exam corpus was higher than that of the textbook corpus. The findings suggest that Turkish high school students who have to learn English with the official textbooks throughout their high school years will have to tackle low-frequency and more sophisticated words at a higher level of  syntactic complexity at the time of taking the nationwide exam. This, in return, creates a negative backwash effect, distorts their approach to L2, and raises other concerns about the misalignment between the official language education materials and nationwide exams.