Sounds to me like a chance to market your services to 30 potential clients. Go into it with the realization that you have potential to sell to 30 prequalified buyers. They all want senior photos, they are all the same age. They will show the results to their parents. You show up in advance with all your gear and make a setup with lights and stuff that they don't normally see. After a bit of tutorial on what you are doing and why each light is placed where it is, you assembly line each girl through and give them some pointers on posing, arm placement, facial expressions, etc. They all mingle around and make funny faces at the subject. In the end, each one signs up with an email address so you can distribute each one a web sized portrait (with marketing materials) as an example of why you should do their portrait shoot.