Currently, corpus-based ESL textbooks are widely utilized as learning materials in various educational institutions where English is taught as a second language or foreign language. These institutions include private high schools, international high s...
Currently, corpus-based ESL textbooks are widely utilized as learning materials in various educational institutions where English is taught as a second language or foreign language. These institutions include private high schools, international high schools, and most universities. Despite the popularity of ESL textbooks as teaching materials, studies related to the ESL textbooks abroad have mainly been carried out with the focus of cultural contents rather than the corpus based linguistics. Hence, this corpus based study has selected a number of ESL textbooks that are commonly used as learning materials in Korea to examine the level of vocabulary, composition, and the suitability of different class objectives. These are five types of textbooks selected for this study: ER, ERAS, LARS, NS, and SS, totaling of twenty three books. Five corpora were constructed and the vocabulary used in the main texts was categorized to analyze the portion and the text coverage of the General Service List, the Academic Word List and the basic vocabulary of Ministry of Education, Science and Technology. Then a corpus-based analysis of the overall vocabulary level of the selected ESL textbooks was conducted to determine the most recommended study material for high school students.
The results of this study are as follows. Firstly, the five types of the textbooks except for ERAS, the distribution of the basic words demonstrates more than 80%. Although the basic academic level vocabulary occupies less than 10% throughout the content, this figure is not considered low compared to most college level textbooks, which contain about 7% to 8% of the basic academic level vocabulary.
Secondly, the consolidated rate of the GSL and the AWL ranges from 86% to 93%. If the learning objective were to require a 98% comprehension of the text, where the learners are able to fully grasp the content of the text without any assistance, they would need to study approximately 10% of the integrated level of the GSL and the AWL.
Thirdly, the portion of the College Scholastic Ability Test(CSAT) level vocabulary is approximately from 87% to 92% in the main texts of the ESL textbooks. This rate is not considered low by any means; however, it is found that for a 98% comprehension of the text learners would require from 935 to 3,842 additional vocabulary. This finding therefore indicates that the ESL textbooks are not suitable to be the primary study materials for the CSAT preparation.
Fourthly, the assessment of the overall vocabulary level of the ESL textbooks based upon the large-scale corpus BNC 14,000. The level of difficulty is found in the order: ERAS, LARS, NS, ER, SS, with ERAS being the most difficult. In order to make a more objective judgement, 22 yearly editions of the CSAT have been constructed and analyzed to verify the level of vocabulary, and the results show that the level of the ESL textbooks proves more difficult than the CSAT.
As a result, this study indicates that the ESL textbooks are good learning materials for improving the general ability to read, write, and speak English but not sufficient enough to be the main study materials for the CSAT preparation. If the ESL textbooks were to be utilized as the class material for senior year students in high school, it is necessary to implement another teaching material for the CSAT preparation, since the vocabulary used in ESL textbooks and those of the CSAT are slightly different.