All of the following have been reviewed by Common Sense Media's Web/App Review site, http://www.graphite.org/
Please note that these apps for appropriate for students K - grade 6, and certainly older.
Google Earth
Cool geographical exploration tool has endless classroom applications
http://www.graphite.org/app/google-earth
Marine Missions
Simple app sets young kids sailing in the waters of ocean conservation
http://www.graphite.org/app/marine-missions
NOVA Elements
Info-packed science resource great for teaching the elements
http://www.graphite.org/app/nova-elements
Bill Nye The Science Guy
Cool app lets kids blast off, bubble, and dig into science concepts
http://www.graphite.org/app/bill-nye-the-science-guy
Where's My Water?
Captivating conservation puzzler focuses on problem-solving
http://www.graphite.org/app/wheres-my-water
Science360 for iPad
Amazing images, videos, and fact-packed text on many science topics
http://www.graphite.org/app/science360-for-ipad
NASA App
Visually super NASA-backed treasure trove may overwhelm
http://www.graphite.org/app/nasa-app
Color Uncovered
Engaging ebook combines art with science in playful ways
http://www.graphite.org/app/color-uncovered
DIY - Get skills. Be awesome.
From cardboarding to cooking, this app helps kids find the fun in DIY
http://www.graphite.org/app/diy-get-skills-be-awesome
Finger Physics
Cute and challenging physics puzzler teaches gravity