Kumon Chinese

Is it good esp. for Int'l school kids.

My son is going to have Chinese lesson by private tutor once a week starting from P.1 (as he's going to Phoenix where they teach Chinese in Cantonese for P.1), but I'm afraid that's not enough practice for him to upkeep his Mandarin (he's having Mandarin lesson everyday now in his kindergarten). I'm thinking if Kumon can help him 'keep in touch' with Mandarin everyday and upkeep his Mandarin standard.

Know that there are quite many int'l school students learning Kumon Chinese, can any mommy share your experience