few/ a few/ only a few

[vil]

Dear teachers,

Would you tell me something about the different connotations of few in the following sentences below?

Few pupils had understood the lesson, so the teacher had to repeat it.

A few pupils had understood the lesson, and they promised to help their comrades who hadn’t.

May I use “only a few” in my wording?

V.

[virus99]

In the first sentence maybe. Few here means "not many", right?

But wait for our teachers to comment...