I was proctoring an exam for a teacher, and I noticed that some students turned their body toward the next person. I felt like they might cheat. So, I wanted to tell them to look straight (take a straight posture) in proper english. Not sure if this is grammatically correct and not awkward to say to my fellow american students. "Please look straight (or straight forward?). Do not turn your body to the side." Thanks so much!

p.s. Also, please point out any grammatical errors in my sentences. :)