Sherpa Prep is by far the best
Sherpa Prep is by far the best GMAT prep service out there. Nafeez and his team are absolute legends, they really take an interest in each student's success, and will help you across the finish line regardless of how much you're struggling. You can take the class a 2nd time free of charge, continue to attend office hours after your class ends, and offer 1-1 tutoring for a fraction of the cost of competitors. They truly embody the non-profit ideology and I can't say enough about Nafeez for everything he does to see others succeed.