'What's our three-word claim?': Supporting English language learning students' engagement in scientific argumentation

摘要

Middle school students in a sheltered English instruction science class are at the beginning of a unit in which they are learning that organisms that are too small to be seen by the naked eye live on and in the human body. (A sheltered English instruction class is an instructional setting in which the teacher attends to students' content learning and English language development.) Specifically, in this lesson students investigate that antibiotics kill bacteria. To start exploring these concepts, their teacher, Ms. Ruttan, asks students to make observations of a photograph of an agar-streak plate test (see Figure 1) to see if they can find evidence of microorganisms living on human bodies. Before students analyze the photograph, Ms. Ruttan informs the class about how the agar-streak plate test was conducted. (Note: This was not done as a hands-on activity because the culturing of any organism is not recommended at the middle school level.) Ms. Ruttan explains to students that a scientist took a cotton swab, grazed it along the palm of her hand, and then streaked the cotton swab along the inside of a pe- tri dish that had been filled with agar (a polymer that contains nutrients to allow microorganisms to grow). Afterward, the scientist placed penicillin disks in the agar plate, sealed the plate to prevent contamination, and let it sit undisturbed for a few days. The teacher further explained that penicillin is a type of antibiotic used to kill bacteria.