Highlighting text is a commonly used technique in history teaching right up to, and including A level. I have spend many a deliriously happy hour on inspection looking through so many psychedelic folders positively glowing with neon yellow highlighter pen. But is this a little too safe as a technique? After all, even if they make a mistake, the text is still there.
What is the alternative? What about using a black felt pen to block out anything that is irrelevant. This is a high-risk activity. Once redacted it is lost forever. Pupils realise this and become more thoughtful before committing. They also tend to seek reassurance from their peers, promoting helpful collaboration.
Much will depend on what you are trying to achieve, of course, but next time pupils or students reach for the dayglow highlighters give a thought to the black too. Less colourful, for sure, but maybe more effective in promoting critical thinking.