10 .
It was ~ at least until fairly recently ~ the tradition within other faiths and denominations, that a young person marked their transition toward adulthood within the faith community at an age broadly commensurate with the bodily changes of puberty. Thus not least do we read of Jesus Himself on a pre-barmitzvah pilgrimage to Jerusalem just as He was entering His teens (though the average age of puberty may well have been rather further into people's teens back then, with less plentiful nutrition and hygiene / medicine). In the Catholic Church, however, it has long been cherished practice for well-pre-pubescent children to partake of their First Communion. Even if you are not yourself a Catholic, you will perhaps have seen gatherings around a girl of (say) 8 years old dressed almost like a bride or bridesmaid, or at least, cherished photographs of such occasions. Such a child is not cognitively mature enough to assimilate the full richness of relevant doctrine, but the following are all insisted on ... apart from which rogue ONE, as usual?
The child must have declared broad acceptance and understanding that what they will be receiving is not 'just bread and wine', and how so
First Communion cannot occur without First Penance (confession), establishing a lifetime pattern of linking these two sacraments
The child must previously have been baptised into the Catholic Church
The child must have attended Confirmation Classes