The present study traces the poor performance of Nigerian students in English to the sole use of British English for teaching and evaluation purposes in the Nigerian ESL classroom thereby neglecting the local Nigerian variations which, as it should be expected, reflect the linguistic and cultural contexts that English must, as a necessary condition, accommodate if it must function effectively in Nigeria’s multilingual socio-cultural setting. The study, after presenting some syntactic and lexico-semantic variations in Nigerian English and highlighting their appropriateness within the Nigerian socio-cultural context, argues that, if students must perform well in English and even in other subjects taught and examined in English, it is necessary to teach them and evaluate their performances by using an endonormative model (that is, Standard Nigerian English), which is capable of reflecting the local variations that English has, in a bid to satisfy the demands for communicative appropriateness, manifested in the Nigerian setting. This is so because Standard Nigerian English as an endonormative model is, because of its ability to appropriately reflect the Nigerian experience, more supportive to the students in the Nigerian ESL classroom than the foreign British model which, though used as the standard in Nigeria as a former British colony, is culturally inappropriate in the Nigerian context and does not, therefore, appeal to the sensibilities of the students who, in their quest for communicative appropriateness in English in the Nigerian socio-cultural setting, have to use the language to reflect the Nigerian worldview.