One Potted Plant, Forty-Eight Students

Use a whole-class demonstration with group observation, not six simultaneous experiments. With one set of material, six groups cannot each manipulate it without chaos. Structure: 5 minutes - students write a prediction to the question, 'If a plant gets food from soil, what should happen to a seedling grown in water?' 10 minutes - teacher demonstrates the potted plant and the polythene bag, and shows a seedling grown in moist cotton; groups observe in sequence while recording. 10 minutes - groups compare predictions with evidence and write one sentence. 10 minutes - whole-class talk using two contrasting claims. 5 minutes - exit ticket: 'What evidence would change your mind?'

Management: assign roles (recorder, reporter, timekeeper), pass the bag along rather than let all students crowd, and keep the black paper and plant on a tray. The visiting coordinator should see students talking from evidence, not a silent copied diagram.

Reasoning: the constraint is material scarcity, so the teacher's judgement is to preserve student thinking, not hands-on activity for its own sake. A demonstration can still be inquiry-based if predictions and evidence talk are built in.

Create a discrepancy the students must explain. The teacher asks: 'If plants eat soil, why does a seedling in cotton and water grow taller while the cotton does not disappear?' Students often answer that soil has 'food' and water has 'food'. The teacher then shows the potted plant's soil level and asks what would happen to the soil if the plant used it as food. This does not prove photosynthesis, but it creates doubt about the soil-as-food model.

Use the evidence, not the label. The teacher should not say 'you are wrong' and give the definition. She should ask students to draw their model before and after, then compare with the seedling. The correct idea - plants make food using light, water, and air - can be introduced as a better explanation of the evidence, with the textbook diagram used after the discrepancy.

Be honest about limits: the seedling demonstration does not prove photosynthesis; it only shows soil is not the sole source of growth. The teacher should say so and plan a longer observation with the potted plant. Reasoning: conceptual change requires that the learner see why the old model fails, not just hear the new one. The exit ticket 'what would change your mind' makes this visible.

Do not pretend to do a controlled photosynthesis experiment that the material cannot support. If the teacher puts the potted plant in the dark for one period and claims it has 'stopped making food', the evidence is not valid; students may learn that science is a performance. Similarly, do not burn a leaf or use iodine without training, ventilation, and safe equipment.

Do not use group work as a substitute for thinking. Putting 48 students into six groups with one plant can produce copying and noise; the teacher should not assume that because students are seated in groups they are investigating.

Do not humiliate the 31 students who held the misconception. The pre-test is diagnostic, not a public confession; sharing the count can make students defend their answer. Do not skip the misconception because the coordinator is visiting; a smooth copied diagram would misrepresent learning.

Reasoning: the teacher's professional judgement is to choose an activity that fits the available evidence and safety constraints, and to protect students' willingness to revise their ideas. The visiting coordinator should see honest inquiry, including its limits.