Here is a teaching strategy that you may already be using, but if not, I highly suggest it. Use online teaching videos (not brainpop or something as catchy, but simple content-based videos) in class as a means to differentiate. A great site for Earth Science is http://www.youtube.com/user/metfan869 (see videos below) Or you could try Khan Academy, or many others.
- Find the video(s) you want to use the teach the content you are trying to teach
- Make a guided note sheet (similar to what you would put in a powerpoint or what you want kids to take notes on
- Include some higher level thinking questions as they go through.
- Then make an application section, or some other activity using the information they they just watched.
Depending upon how you want to run the lesson, you could make the application task homework if they don't finish, make different levels of application questions etc. People will finish at vastly different times, but hopefully they all finish and grasp the main points of the content. That's why we are here, right?!
Have you ever used a similar strategy in your classroom? If so, how did you do it? I also found this to work well for review when the topic was familiar, but some needed instruction again and some just needed reinforcement.