The fourth chapter of the Khuddakapāṭha (Khp.2). It consists of ten questions which, according to the Commentaries (KhpA.76; ThagA.i.479), the Buddha asked the young Sopāka, then an Arahant though only seven years old, with the idea of giving him the higher ordination (upasampadā).
The boy-Arahant answered the questions and this conversation formed his ordination. (See also Thag.v.485; Ap.i.64 f). These questions were elaborated by the nun Kajaṅgalā (q.v.) (A.v.54 ﬀ).
The Majjhimanikāya Commentary (MA.ii.636) on the Ambalaṭṭhika-Rāhulovāda Sutta seems to indicate a set of questions called Kumārapañha in connection with Rāhula when he was seven years old.
See also SA.iii.99, where Buddhaghosa says that Citta-gahapati, in a discussion with Nigaṇṭha Nāṭaputta, referred to the Kumārapañha.