... from Joe on exercises for high school students:
(1)  I have completely updated and revised one of the most popular lessons in the ArcLessons library, “Exploring 10 Landscapes”  (OK, it’s actually 11; I couldn’t bear to dismiss one! ) -
http://edcommunity.esri.com/arclessons/lesson.cfm?id=529
Data set here:
http://www.arcgis.com/explorer/?open=f64a0772c5ab472f80332e9285ef125c
In this lesson, you will use ArcGIS Online to investigate 11 topographic map features and their surrounding landscapes. Objectives: Work with topographic maps, including features, elevation, measurement, and other aspects of these maps to understand physical and cultural processes and the results of those processes. All you need is a Web browser. Level: 5 Questions for 11 landscapes = 55 questions total. Students need to be familiar with topographic maps and some basics of physical and cultural geography to most effectively use this lesson.   
Landscape 1:  Sand Dunes                                                           
Landscape 2:  Karst                                                                         
Landscape 3:  Eskers                                                                                      
Landscape 4:  Plate Tectonics                                                     
Landscape 5:  Swamp                                                                    
Landscape 6:  Glaciers                                                                   
Landscape 7:  Rivers                                                                       
Landscape 8:  Railroad-Influenced Towns                             
Landscape 9:  Modified Coastlines                                           
Landscape 10:  Volcanoes                                                            
Landscape 11:  Protected Areas                                                
Answer Key                                                                 
Activity: Students can work independently or in groups through each of the 11 activities. They could choose one of the 11 areas featured to construct a written report and/or an oral presentation to the class about the area they select. Revised 19 August 2011 with improvements and answer key. Updated: 11 May 2012.
(2)  New lesson and data set on investigating the Harrisburg 29 February 2012 Tornado:
http://edcommunity.esri.com/arclessons/lesson.cfm?id=715
Post-tornado imagery (thanks to the folks at GeoEye) and pre-tornado and other data on ArcGIS Online here:
http://www.arcgis.com/home/webmap/viewer.html?webmap=9d74088e35de470c90c9664a18fb394f
 
Joseph Kerski
Joseph J. Kerski, Ph.D.| Education Manager
Esri | 1 International Court | Broomfield CO  80021-3200 | USA
Tel 303-449-7779, ext. 8237 | Fax 303-449-8830
jkerski@esri.com | esri.com
Twitter:  @josephkerski