In paragraph 3, the author used the phrase "guided his charges" to show that the teacher was a trusted advisor and role model for is students.
The reason for the phrase
In the story, we learn of a tutor named Darlington who guided his students as they visited some important humanist scholars. On their way, the narrator describes this tutor as having "guided his charges." This might have been a reference to his role as someone beyond a teacher.
He made sure to guide his wards. Another reason for this phrase would be to convey the teacher's role as a person in authority over his students.