Final answer:
Highlighting has not been directly found to increase student performance on exams, while other reading strategies like summarizing, self-testing, and mnemonics have been shown to be more effective.
Step-by-step explanation:
The reading strategy that has not been directly found to increase student performance on exams is b) Highlighting. While highlighting can help with memorizing main ideas, it does not promote critical reading or deeper understanding of the material. Other reading strategies like summarizing, self-testing, and mnemonics have been shown to be more effective in improving exam performance.