From the one side, classmates have a significant influence on child's behavior and his or her success in school. First of all, children spend much time at school. Classmates have many things in common such as age, interests, homework and classes after all. So, they discuss their impressions about a new teacher, solve problems together, learn their homework, gain new knowledge and experience and even make their own discoveries. Sharing all these makes them closer. Some of them become friends and they spend after-school time together. In addition friends tend to copy each other's habits and manners. For instance, my little sister became friends with the girl who did not have good grades at school at that time. It does not mean she could not have better grades; she just had many friends who did not care about their grades. So, when they started to spend their time together and share their interests, girl's grades improved. They did their homework together, shared their dreams and exciting moments. From this point I must agree that classmates can change child’s attitude towards school.
From the other side, parents have a great influence on children' success in school too. For example if parents show an interest in their child's progress and talk to him or her about the importance of learning I think their child will listen to them and do his or her best.
Personally, I believe that relationships between parents and a child play an essential role in child's success in school. If these relationships are close and wholehearted I am sure that parents should not be afraid of bad influence from the outside.