The best solution. You don't have to worry. Just you try to open your heart and try not to use the phone if necessary. When it is time to time to be useful, such as homework.You need to set the rules in the class. If someone did to get punishment is if someone play phone while the teacher was teaching to seize the phone and money were 20 baht. After 1 hours return phone calls.Will the around money is 2 imaginable. And add hours to seize the phone. Just as you know to use the phone in a reasonable time.