Brenda Graminski found CK-12 Foundation:

• Significantly improves attainment“Can be used on any device so more equal access”
• Moderately builds student knowledge“The adaptive practice, and engagement with text.”
• Significantly improves teaching efficiency and productivity“Scoring adaptive practice, quantifying engagement and grading quizzes.”
• Moderately reduces teacher workload
• Moderately saves school money“It's a free resource and easily accessible.”