Some recommended "kid-friendly" web search engines are below. Please note that children should always be supervised by an adult when using internet resources. "Kid-Friendly" or "Kid-Safe" is a label entered by a company selling or promoting their product, not a level of protection for your child's online safety.
When students are looking for help in searching the web, very often they are looking for pictures to use in a project. My top three picks of copyright-friendly image searches are below.
Pics4Learning (by Tech4Learning.com)
Pics4Learning is a safe, free image library for education. Teachers and students can use the copyright-friendly photos and images for classrooms, multimedia projects, web sites, videos, portfolios, or any other project in an educational setting.
Google Images Advanced Search, filtering by "licensed to reuse"
Flickr Advanced Search, filtering by Creative Commons licensing