Local languages are used as the languages of instruction in elementary schools, with French only introduced after several years. In wealthier cities, however, French is usually taught at an earlier age. At the secondary school level, local language is generally forbidden and French is the sole language of instruction. Beninese languages are generally transcribed with a separate letter for each speech sound (phoneme), rather than using diacritics as in French or digraphs as in English. This includes Beninese Yoruba, which in Nigeria is written with both diacritics and digraphs. For instance, the mid vowels written ''é, è, ô, o'' in French are written '''' in Beninese languages, whereas the consonants are written ''ng'' and ''sh'' or ''ch'' in English are written ''ŋ'' and ''c.'' However, digraphs are used for nasal vowels and the labial-velar consonants ''kp'' and ''gb,'' as in the name of the Fon language ''Fon gbe'' , and diacritics are used as tone marks. In French-language publications, a mixture of French and Beninese orthographies may be seen.