You can use the same theme for students in many age groups as long as each lesson and activity is age appropriate. For example, if you're using a winter theme for kindergarteners, you'll want to set up a winter-themed play area and have arts and crafts projects using snowflakes and snowmen. This would be the ideal time to teach the children what ice is and allow them to play with it while it melts so they can see it actually is frozen water. For older children, you could explore the properties of ice and discuss the differences between solids and liquids.
For thematic teaching to be effective, it should encompass all the subjects the students are studying, or at least as many of them as possible. If your theme is roller coasters, post pictures of roller coasters around the room, do roller coaster-related math and work on some of the physics concepts that are necessary to design a roller coaster. Look for ageappropriate stories about roller coasters for English, or have each student design his own roller coaster and write a story about it.
Although learning is serious business, children who have fun while learning learn better and retain more information. Make sure your themes will appeal to the students and incorporate games, fun projects or activities into your lesson plans to make the lessons more enjoyable. If possible, decorate your classroom with theme-related décor or have your children help you create the decorations and hang them throughout the room. Choose topics that will appeal to your students and are relevant to what is going on in entertainment, politics or current events.
Themed lesson plans should be long enough to teach all the important topics, but shouldn't be so long that students lose interest. You'll need to judge the amount of teaching material you have to determine the best length, but it's best to switch themes monthly if not more often. Lessons shouldn't be shorter than two weeks either or you'll have to come up with too many themes throughout the year.