Two pieces of evidence that Martha's grandfather is wise in The Scholarship Jacket are first when he refused to pay fifteen dollars for the scholarship jacket because for him it is supposed to be earned and not bought. Otherwise it's not a reward. This made the principal change the decision and give her the award. He took a stand for what was right and the result was Martha got the scholarship jacket.
Second evidence is the fact that the child was aware of the hardships at home. She knew she was poor and dependent on her grandparents. She was told to work hard to reap awards.She used to do household work. It shows that the child was raised in the right manner. She couldn't understand Racism and favouritism but her grandfather could and so he refused to pay for the amount. She listened to her grandparents even when she didn't want to and was angry. This shows she was raised wisely by her grandfather.