To ensure you get the most out of your time, have an idea of what outfits you would like to wear. Practice some poses at home and bring screenshots of poses you would like to take inspiration from. Arrive warm and stretched with your first outfit on. Don't forget your smile!
The best way to ensure photo days run smooth and on time is to have a teacher assigned to posing students. It is a great idea to have classes work out their group poses in class the week prior and take photos to remind you. For solo photos work with your students beforehand on pose ideas. For little ones it is easy to have 1 or 2 set poses, older students can get creative and show off their strengths!
You often hear dance teachers say they want picture moments, where you hold that leg extension long enough for someone to take a photo, and that is exactly right! To ensure you get great stage photos make sure you are holding those moments and using your facial expressions.