As soon as I walked into Celia Rojas’s prekindergarten class in Union City, N.J., I was sucked in by the hum of activity. Art plastered the walls, plants were hanging from the ceiling, and in every nook there was something to seize a child’s imagination. Some kids were doing cutouts of paper clothing and others were at an easel, painting. A bunch of children were solving puzzles on a computer, while another group was building a pink cardboard chair, which they called “A Chair for My Mother.” In the reading nook a girl was learning about how, when the wasp larva hatches, it eats the spider. Three classmates were playing dress-up, trying on old felt hats and checking themselves out in the mirror.

The teacher was everywhere — praising kids, offering suggestions when they were stumped and, sometimes, peacemaking. Two boys were peering at insects through a microscope when they started fighting over who got to look next. Ms. Rojas deftly diverted them. “How many parts does an insect body have?” she asked. The boys knew: “Three parts — the antenna, abdomen and legs.”

“How about an insect salad — would you want to eat it?” she inquired. “Ugh,” the boys chorused. “Why not — are they bad for you?” she asked. The boys thought about it. “Maybe if you chopped them up they’d be O.K.,” one volunteered.

At that moment I wished that I were 4 years old and could join the festivities.

But most pre-K classrooms look entirely different. After surveying preschools nationwide, Robert Pianta, dean of the University of Virginia Curry School of Education, concluded that “superficial task demands, including giving directions and assigning routine tasks, predominate over children’s involvement in appropriate conceptual or class-based activities.”