I couldn't help but wonder what classics besides A TREE GROWS IN BROOKLYN might be looked down on if they had been categorized as YA. Graham seems to make a distinction between work written about teens and for them, but is there really a difference? I write what I like. It happens to be about teens. Agents, editors, publishers, and booksellers tell me what market they will sell my work into. I never set out to write YA literature. I set out to write for me. In one age it might have been classified as science fiction, today, the tendency is to label it YA dystopian. To me it doesn't matter.
Read whatever you want, and never be embarrassed about what.