Melinda's a bit irritated with Mr. Freeman. He is extremely negative about her tree, and she has to agree with him.
She thinks she should be banished from art class, so she won't get in the way of "real artists […] like Ivy" (71.2).
Tears in her eyes, Melinda throws away the linoleum on which she was carving her tree.
Mr. Freeman takes her work out of the trash, brings her tissues, and encourages her to keep trying. He wants her to give her tree "flaws" to make it "interesting" (71.3).
If Mr. Freeman believes in her, she'll keep trying even though it's hard.