Many teenagers have their own smartphone. What are the advantages and disadvantages of this and give your opinion?

Having smartphone for teenagers is useful around their environment, being the advantages, while some people argue that adolescents having smartphone can bring harmful to them. Also, I believe this leads to effect for their performance in schools. Initially, a gadget ownership for many teenagers leads them away from crimes, leading to their parents will feel cozy when they leave their children outside their guard. However, other people consider that those tend to depend on their smarphone, resulting to ignore the people around them. The research study of Indonesia in 2020 found that more 75% of teenagers used the GPS in their smartphone to share their location to parents when they were kidnapped. On the other hand, my nephew is difficult to be controlled due to playing games in his smarphone, and he does not obey their parent. Granted, many young children use smartphones, especially for lessons at the schools, leading to get good impact on the development of their learning pattern. This is because they get a wider range of learning resources than the teachers in their schools, comparing the suitable learning for them. For instance, in North Sumatra, there are 80% of schools allow students to bring smartphones, while the teacher runs out of explaining lessons, like mathematics, and the teacher ask students to open Youtube to find the same questions in other ways, and if they are more suitable to follow the method of that platform, the teacher will welcome it. To conclude, having own smartphone in young children will bring benefits, although there are those who argue the reverse. Albeit I believe that bringing a smartphone will improve children's ability to learn at schools. Are there other ways to improve those other than carrying a smartphone?