Recommended Reading: Productive Math Struggle: A 6- Point Action Plan for Fostering Perseverance by John J. SanGiovanni, Susie Katt and Kevin J. Dykema.
In this 7 minute video from Visible Learning for Mathematics, rigor is defined so you can evaluate tasks.
Place Value Tasks Ep 225 of Math is Figure-Out-Able a podcast by Pam Harris and Kim Montague
YouCubed a website by Jo Boaler's group at Stanford with lots of rich tasks
Three Act Tasks: A whole group task split into three parts. The first act poses an engaging and perplexing problem. The second act includes information and solution seeking discussions. Finally the big reveal in the third act!
Number Strings: Guide the class through a series of problems that allow students to figure out the math on their own!
Esti-Mysteries: A rich task by Steve Wyborney where students use clues to make reasonable estimates.
Open Middle: Challenging problems that have more than one right way to solve them.
Julia Robinson Mathematics Festival Puzzles: All the printable math puzzles you could want!
Inside Problem Solving from Inside Math: Tasks sorted by grade.
Tang Math: Lots of free resources for teachers to use, others available with a paid subscription. Includes skill games, learning games, and picture books. Tangy Tuesday and Wordy Wednesday sample packs available under 'puzzle subscriptions.'
KenKen Puzzle: Sudoku and other daily challenges
Solve Me Mobiles: Student must balance the mobile by exploring possible values of the shapes.