If you want to use the lamp analogy, as in your question, then students are simply sitting and not illuminating, which they can only do through the acquisition of knowledge. To take it a step further a student who does not take advantage of learning opportunities, may be compared to a lump of coal--great potential, but it has to be ignited.
A student has tremendous potential, but until the switch is turned, or the wick is ignited, the student will remain in a dormant state. Once a source of knowledge is supplied, the student will illuminate and be productive.
I don't agree, in general. Good students already burn brightly with life when they come to the studio or classroom; the teacher may bring additional fuel, clear the chimney, or shelter the flame, all of which may be helpful, but is nurturing rather than generative.
Perhaps there are times when an inspiring teacher can actually, in some sense, light a flame. But I think these are comparatively rare.
I do not disagree, however, I have seen students with knowledge, waiting to be ignited but for social reasons, economic reasons, prejudice, etc, that student is often overlooked. Also, our cookie cutter approach to eduction misses some students.
Perhaps it means that the students are like lamps which are filled with lighting fluid (filled with knowledge). After their flame is lit, then others will see that they are willing to share that knowledge.
Cuz their own flames went out during years of being forced to sit in desks listening passively to teachers, who did not encourage interests and did not ignite or encourage them. Students have flames of joy and interest in life. These flames should be allowed to burn brightly during the formative years.