My teenage son Karl became withdraw after his father died. As a single parent, I tried to do my best to talk to him. But the more I tried, the more he pulled away. When his report card arrived during his junior year, it said that he had been absent 95 times from classes and had six falling grades for the year. At this rate he would never graduate. I sent him to the school adviser, and I even begged him. Nothing worked. One night I felt so powerless that I got down on my knees and pleaded for help. "Please God, I can't do anything more for my son. I'm at the end of my rope. I'm giving the whole thing up to you." I was at work when I got a phone call. A man introduced himself as the headmaster. "I want to talk to you about Karl's absences." Before he could say another word, I choked up and all my disappointment and sadness over Karl came pouring out into the ears of this stranger. "I love my son but I just don't know what to do. I've tried everything to get Karl to go back to school and nothing has worked. It's out of my hands." For a moment there was silence on the other end of the line. The headmaster seriously said, "thank you for your time", and hung up. Karl's next report card showed a marked improvement in his grades. Finally, he even made the honor roll. In his fourth year, I attended a parent-teacher meeting with Karl. I noticed that his teachers were astonished at the way he had turned himself around. On our way home, he said, "Mum, remember that call from the headmaster last year?" I nodded. "That was I. I thought I'd play a joke but when I heard what you said, it really hit me how much I was hurting you. That's when I knew I had to make you proud." By saying "Karl became withdrawn", the author means that the boy changed entirely and   _  .
preferred to stay alone at home often escaped school refused to talk to others began to dislike his mother