What did Auggie miss about being a baby?

Auggie often acts like a baby in the beginning chapters of Wonder and knows that when he behaves in this way, his family will continue to treat him as a baby. When his mother first mentions the idea of him going to Beecher Prep instead of being home schooled Auggie says, "I admit: I made my voice sound a little babyish." Auggie purposely engages in this babyish behavior because he knows that his family is very protective of him, and making himself seem younger and more vulnerable is a way that he is able to get what he wants from them.
Though Auggie purposefully acts babyish in the early chapters, he mentions wishing he was still a baby in the chapter called "Driving." His parents are in the front seat of the car discussing whether they should send Auggie to middle school rather than continuing to homeschool him. Auggie wakes up in the backseat and overhears his parents debate. He expresses that he is concerned about going to Beecher Prep because of how different he looks from other kids. His mother mentions that they had previously toured the science lab and saw baby chicks hatching. She begins to compare the baby chick to Auggie when he was a baby. Auggie says, "I miss being a baby, not knowing stuff."
Auggie has a facial condition called Treacher Collins syndrome, which causes his face to look quite different from a typical person. Throughout his life, Auggie has dealt with people staring at him or, more often, staring away from him because of his appearance. When Auggie is a baby, and even a toddler, he doesn't know that he is different from everyone. His family works hard to protect him from feeling different. As Auggie gets older, he starts to notice that he is being treated differently from other people because of how he looks. Children comment on his appearance or even run away. Adults look at him and often immediately look away. When Auggie says he misses "not knowing stuff," it is likely that what he misses is not knowing how different he is. He misses being protected by his family from feeling different. When he was a baby, he had no idea about the struggle his life would be because of what he looks like.