1.Ixl.com
Rank:3,223
Worth:$2,100,000
DA:72
IXL is the world's most popular subscription-based learning site for K–12. Used by over 14 million students, IXL provides personalized learning in more than 9,000 topics, covering math, language arts, science, social studies, and Spanish. Interactive questions, awards, and certificates keep kids motivated as they master skills.