To give them more concern and encouragement is an effective way(It is better to write in an active voice. There are useful words for showing your opinion like “I would say that '' ) . On top of that students might be underachieving because of the lack of interest in learning. It might happen because of the teacher giving them boring lessons , the teacher couldn’t activate the class environment. Speaking of that, I came up with an idea. You know most adults show that they have regretted that they didn’t work hard when they're in school and cannot realize the importance of studying until they experienced or suffered losses. So could we let the teenagers go to work first for one year or two then ask them to choose whether they choose work or studying! Once they experience and realize it, they can be self-disciplined and have the willpower to behave(probably act)!