I think the first thing to help them is to figure out the reasons why they underachieved. If the students wanted to get a good score and they studied hard to achieve it but they failed, I think tutoring classes can help them to better understand lessons. We can also let them communicate more with the top students to get some effective learning methods. But if the students underachieved because they didn't even care about studying, I think the key point is to lead them to first find the motivation to study. Well done July. Nice writing. A few small changes. “Let them” doesn’t need a preposition after. And I’ve slightly changed the last sentence for you, a more natural sounding syntax.