10 Things I Hate About You is a 1999 teen comedy directed by Gil Junger, starring Julia Stiles and Heath Ledger. It's arguably one of the more thoughtful examples of the genre, not just because it's based on a Shakespeare play, and actually features a lot of Shakespeare quoting through the characters. But there are more quotes!
The posters in the classroom where a lot of scenes take place have aphorisms by famous intellectuals on them. The most prominent quote can be seen in each classroom scene right at the front, and it's from Albert Einstein:
What is popular is not always right; what is right is not always popular.
The second quote is at the back of the room and is only once shown clearly, from Philip James Bailey:
OF ALL FRAUDS
The third one is never shown clearly and completely, but it's most certainly this quote from Mark Twain: