My teenage son Karl became withdrawn after his father died.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. In this way he would never graduate. I sent him to the school adviser, and I even begged him. Nothing worked. * One night I was at work when I got a phone call. A man introduced himself as a head teacher. " I want to talk to you about Karl's absences ." Before he could say another word I choked up . And said sadly, " I love my son. 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 head teacher seriously said, " Thank you for your time." * Karl's next report card showed a marked improvement in his grades. He was even on the list of the best students at school. In his fourth year, I took part in a parent-teacher meeting.I noticed that his teachers were surprised at the way he had turened himself around. On our way home, he said, " Mum, remember that call from the head teacher last year?" I nodded. "That was me. I thought I'd play a joke but 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." , . (5) Who telephoned Karl's mother that day?
The head teacher. The school adviser. Karl himself. The passage doesn't tell us.