Pawley and Syder (1983) pointed out that idiomatic expressions can be discussed in terms of nativelike selection (NLS), which refers to the ability of the native speaker to express his/her intended meaning using an expression that is not only grammatical but also nativelike. In the current study, Pearson’s correlation coefficients were used to investigate the possible correlations between the variables of language contact (LC), language attitude (LA), and language motivation (LM) integrative (Int.M) and instrumental (Inst.M), age of L2 onset (AoO), and length of exposure to target language (LoE) and English bilinguals’ (EBs) knowledge of NLS in an international school—a semi-naturalistic setting. A possible correlation between EB’s NLS scores and their English academic performance (EAP) was examined as well. Moreover, multiple regression analysis was conducted to investigate the factors predicting EB’s NLS knowledge. The participants were 281 high school students of mixed gender and ethnicity from an international school in the Philippines. Different questionnaires were used to collect data related to LC, LoE, AoA, LA, and LM. Data concerning NLS knowledge and EAP were gathered using a receptive NLS test together with a standardized English test. The results of the correlation analyses indicated that the variables of LC, LoE, Int.M, and AoO were significantly related to EBs’ knowledge of NLS. Moreover, a significant positive correlation was found between EB’s knowledge of NLS and their EAP. The results of regression analysis yet revealed that the variables of LC, LA, and Int.M predicted EB’s NLS knowledge. The findings provided pedagogical implications for those involved in EFL/ESL teaching, particularly in international schools.