Which two things are the children compared to at the beginning of the story "All Summer in a Day"?

As the story opens, the children are first compared to roses and weeds, intermingled, looking out a window. They are anxious for a glimpse at the sun that has not been out on Venus for seven years. As Bradbury puts it:

The children pressed to each other like so many roses, so many weeds, intermixed, peering out for a look at the hidden sun.

This is an apt simile (comparison using the words like or as) because, as we shall see, the children have divided themselves into two groups: the roses—the popular children, like William—and the weeds, the unpopular children, like Margot. It is also an appropriate simile because, like growing plants, children need and yearn for sunlight.
Later, as the sun begins to emerge, the children are likened to "a feverish wheel, all tumbling spokes." That is, they are all responding as one except for Margot, who stands apart from the group. This foreshadows how the rest of the children, jealous because she has already seen sunshine, lock her in the windowless closet when the sun comes out.