You want to stimulate the interest of your students.
The Easter holidays are close and you want to keep the interest of your students for their studies in a way full of fun. During the holidays send one SMS per day asking intelligent questions from the curriculum. The students will send their answers via SMS and when they return from vacation the winner will get his gifts.
Use a combination of Web2SMS and Premium SMS service that allow you to send bulk messages and then receive the replies sent by the users.