It's not just a child who recites it. Anyone remembering a loved one says it. It's called the Kaddish (קדיש)

Here it is in Transliteration:

Yitgadal v’yitkadash sh’mei raba b’alma di-v’rachirutei, v’yamlich malchutei b’chayeichonuvyomeichon uvchayei d’chol beit yisrael, ba’agalauvizman kariv, v’im’ru: “amen.”Y’hei sh’mei raba m’varach l’alam ul’almei almaya.Yitbarach v’yishtabach, v’yitpa’ar v’yitromamv’yitnaseh, v’yithadar v’yit’aleh v’yit’halal sh’meid’kud’sha, b’rich hu,l’eila min-kol-birchata v’shirata, tushb’chatav’nechemata da’amiran b’alma, v’im’ru: “amen.”Y’hei shlama raba min-sh’maya v’chayim aleinuv’al-kol-yisrael, v’im’ru: “amen.”Oseh shalom bimromav, hu ya’aseh shalom aleinuv’al kol-yisrael, v’imru: “amen.”