Earthsearch (1981)? Originally a BBC radio series, which later got a novelization.
The main difference with your recollection would be that there are several children, not just one.
Three crew-generations previously, the starship Challenger - a vast ten-mile-long survey vessel – was launched from Earth on an interstellar mission to search the universe for an Earth-type planet to colonise. This has been unsuccessful, and the ship's once enormous crew-count has now been reduced to four. Telson (the ship's Commander), Sharna (Science officer), Darv and Astra are the third-generation crew- the only survivors of the disastrous Great Meteoroid Strike which seriously damaged the ship two decades previously, killing the entire second-generation crew and rendering large areas of the ship "uncontrolled" and inaccessible to its electronic systems.
From infancy, the four third-generation crew members (now in their early twenties) have been raised by robots and by the Angels – mysterious unseen beings who run the ship and who only manifest as disembodied voices. Darv, the most sceptical and enquiring of the crew members, suspects that the Angels are merely computers; but the others consider them as "Guardian Angels" and work entirely under their guidance. [...]
Unrevealed to the crew, the Angels (who are the ship's control computers; their name being an acronym of ANcillary Guardian of Environment and Life ) have their own agenda. They desire absolute control and mastery over any colony resulting from the mission. To this end, they covertly engineered the apparent accident which killed the second-generation crew (who would otherwise have ended the mission before the Angels wanted it to end) and have kept the third-generation crew sexually immature and innocent via drugs and disinformation in order to keep them more tractable. However, their machinations have begun to backfire already. [...]
Earthsearch eventually reveals itself as an inverted creation myth, providing a possible "factual" story which could lie behind various Earth legends. The story deliberately misleads the listener in order to gradually reveal that the planet Paradise is in fact the Earth of human history as we know it (with the original "Earth" being a previous forgotten homeworld for the human race) and that the legends of authoritative and fear-inducing "angels" refer to the domineering computers.
Found by searching this site for
[story-identification] computer angels which brought up, among others, British Radio serial with a tyrannical computer looking after a teen boy and girl on a spaceship (although I could have remembered previously identifying it for Radio drama with four kids in a spaceship returning to a missing Earth ...).