K5 Learning
This site has a few practice worksheets designed for students from Kindergarten to Grade 5.
Khan Academy
This organization has resources for reading and designed for students from Grade 2 to Grade 9.
IXL
This website has worksheets and activities to complete from Pre-K to Grade 12. The website has multiple topics on English grammar and is a great resource to use when tutoring.
English Club
This site has multiple reading exercises and worksheets designed to help the 4 language skills of Listening, Speaking, Reading, and Writing.
Agenda Web
This site has pdf worksheets for reading comprehension. The site is divided into three levels: Elementary, Intermediate, and Advanced levels.
15 Worksheets
This site has multiple free worksheets available to you ranging in various topics from reading, writing, grammar, math, etc. Each topic contains 15 worksheets and is a great resource to use when tutoring.