Babysitting

So, I have a babysitting job. I pick up a little boy every weekday after school several blocks away and take him to a McDonald's a couple of metro stops away and wait for his dad to pick him up from there. Sounds easy right? It isn't. He is driving me insane. The first day he was wonderful, compliant and polite. Then, he started becoming difficult and disobedient, making it hard for me to keep an eye on him, or keep him near. I've considered quitting over and over again, and I've only done this three times. It's ridiculous. Unfortunately, the pay is decent, so I don't want to quit. I'd like the extra spending money. So, I'm staying. And desperately hoping he calms down.