A young adult (YA) book I read in the late 90s:
The main character is a teenage girl. She lives with her mother and younger sibling. She lives in poverty/school outcast.
Three events from the book:
Something about the younger sibling having a pee accident and the vivid description from the teen
Something about eating cereal for dinner
At one point, her family gets a bag of free clothes, which she is really excited to wear to school even though it’s stained. Might be leather skirt and white sweater?
A bit of a long shot, but there’s some overlap with The Pickle Song by Barthe DeClements (1995).
I think I remember something else. I think the main character’s younger sibling was about 5 and had a developmental disability.
Was it something about a white stuffed unicorn? This sounds familiar to me, and I know I had a similar book in the 1990’s that I initially bought because I thought it was about unicorns, and then it was about a similar situation as you are describing. I can’t remember the title, either, though!
Could it be Class pictures by Marilyn Sachs?