Mother Tongue Education (MTE) in the Philippines seeks to educate learners from kindergarten to 3rd grade using their mother tongues. However, in Linguistically Diverse Contexts (LDCs) where multiple mother tongues are spoken, a lingua franca is nominated as the alternative MOI. Against this backdrop, our study explores the language attitudes of multilingual learners and parents towards the mother tongues and Tagalog. We argue that the use of Tagalog may challenge and locate local languages in LDCs especially in mother tongue-based classrooms. After conducting individual interviews, we found that the learners have overwhelming use of Tagalog over mother tongues. Meanwhile, parents highlight their age-specific use of their mother tongues which are predominantly spoken with adult speakers. In addition, both groups favour the use of Tagalog as the MOI in the classroom to accommodate the multilingual population, not because they hold negative attitudes to these local languages nor do they reproduce the myths that subvert the use of these languages in the academe. However, favourable attitude to the lingua franca may eventually pose challenge both in the local languages and the MTE itself. For the latter, it may not live out to its promise to engender local languages through the language-in-education policy.