One issue holding back the adoption of Hepburn has been that the standard national curriculum (gakushū shidō yōryō) calls for all children to be taught romaji beginning in the third grade (previously fourth grade) of elementary school. It's taught in Kokugo (national language, i.e., Japanese) classes and included in those textbooks, as romaji characters are used in Japanese alongside kana and kanji as well as, increasingly, in daily life (user names, passwords, etc.). At that age, native speakers of Japanese can acquire kunreishiki more easily, as the consonant representation corresponds more closely to the Japanese phonology that they have internalized.