I’m teaching two writing courses and I’m giving a diagnostic writing in each. They write an sample essay. However, I found out a tremendous amount about my student’s vocabulary with a simple vocabulary activity that I did in class. I gave them various vocabulary lines like scorching……. freezing in which I asked them to add words in between or at the ends such as scorching…boiling…hot…cool…frosty…icy…freezing. I gave them four other opposite lines to do. I could quickly tell who had an indepth vocabulary and who will probably have difficulties in expressing themselves. I walked around as they were doing the vocabulary sheets and recorded my observation. Next class, I will have to do activities to help them enlarge their vocabulary so they can be expressive writer
What quick diagnostic tests do you do in your class that give you powerful results
Education with Technology Harry G. Tuttle 
Having students write a sample essay is one way of assessing students’ vocabulary skills. But having a prepared exercise like the one you suggested is better. Another suggestion is the use of context clues exercise. You can prepare a set of 15-20 sentences. Each sentence must use a difficult word, underlined. Students guess the meaning of the word based on the context of the sentence. This exercise is good for practicing their critical thinking skills.
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