Provavelmente, "Infinity Jinx" (2005), de Margaret Peterson Haddix, coletado em Inesperado : 11 histórias misteriosas . A tampa toca um sino?
Encontrei-o pesquisando neste site por [story-identification] learn read children que retornou ID da história: menino que está preso aos 5 anos com o robô babá que corresponde muito bem à sua descrição.
Um cientista introduz uma vacina para impedir que as crianças envelheçam, para que os pais nunca tenham que sofrer a perda de vê-los crescer e sair de casa.
Da pergunta acima:
The injection/serum used to halt the aging process was developed by a scientist, who when he first shared his findings had a 5 year old son and injected him, then told the onlookers/potential buyers/other parents to come back in 20(?) years. When they did, their children were adults and no longer needed them or were ungrateful layabouts, and the scientist's son was still 5 years old, cute, needy, etc.
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When a child whose aging process has been stopped learns how to read, they begin aging normally again, so the parents don't want them to learn to read.
A personagem principal é uma mãe que vive num complexo de apartamentos e faz quase a mesma coisa todos os dias com a sua criança sem idade.
Talvez você tenha confundido a babá com a mãe? Na revisão vinculada na resposta anterior:
When mommy and daddy are at work, the robot-nanny is there to care for him by cooking, cleaning and guarding the door when the doorbell rings until the person leaves.
Um garoto rebelde no complexo apresenta essa criança aos livros.
Também da revisão:
It’s a boy, taller than him and a face he hadn’t seen before. Curious he opens the door just a tiny bit and alarms burst into sound and the robot-nanny races over to close the door and place him back to the safe security of the couch. Only she didn't. The strange boy rushed in and to her back and she stopped moving. This is the start of Timmy’s adventure as he learns about learning, reading, writing, counting and many other things we find so commonplace and bring. He learns how to read the clock on the wall and basic books. He also learns he is hungry for more knowledge. Timmy wishes to grow.