Main idea is a very important concept for kids to understand. If they can't understand main idea, then what's the point of even reading!? I can't tell you how many excellent readers I've seen in my short time teaching that can't seem to get anything out of their reading. They couldn't even tell me what they read about.
In light of that, here are some activating strategies for teaching main idea.
Using word webs and concept maps are great tools for introducing concepts in the content areas or even a theme for one of your read alouds. Having kids brainstorm anything they know about the subject really jumpstarts the thinking process.
Predict a Passage is another good way to introduce the concept of main idea. The focus of this strategy is to predict what the story is about, read the passage, and then correct any misconceptions at the end.
Another strategy is "The Main Idea Envelope Please." Give students envelopes with either a topic sentence, supporting detail, or a main idea on the front. Inside will be a card with the correct response folded so it cannot be seen through the envelope. Have the students go around the room and see whose envelopes belong with their group. Once the students have found their group, they are to read their envelope and discuss which one is the topic, supporting detail, and the main idea. They are to give reasons for their choices. Then, they should say which one they think they have (topic sentence, supporting detail, or main idea. Once the prediction has been made, the teacher announces, "The Envelope Please." This is the signal for the students to open their envelope and see if their predictions were correct.
I was also thinking that a Carousel Brainstorming is a good way to get students thinking about the main idea of a content area. In Social Studies, we are about to start a unit on South Carolina in the 19th and 20th centuries (Jim Crow Laws, new technologies, mill villages, The Great Depression, and the New Deal). I decided to paste pictures related to each topic on posterboard and laminate them. I will have students carousel around the room to each photo making comments with white board markers or sticky notes. (Reusing materials is always a plus and a timesaver!) Having them jot down their "thinkings," inferences, and comments about each photo is a good way to see what they already know and to get them interested and thinking about the new topic.
If you know any other good main idea strategies, please share with us!