If you are contemplating buying your teacher gifts, take your time to get the best one possible. Interestingly, the best one need not be the most expensive. On the contrary, too expensive gifts can sometimes be counterproductive and may convey wrong intention. Well thought out gifts in contrast can be inexpensive, but such things are sure to impress your teacher more. Therefore, first try to find what your teacher will like to have as gifts.
Do not ask him/her directly; but do try to find out through casual talks or simply by watching his/her movements or the things that he/she uses. If that is impossible, here are few suggestions you can consider. Pens and books are something which every teacher will need in his day-to-day profession. You can probably gift him something of that stuff. Perhaps even a pen stand will be an ideal gift for your teacher.
A teacher like many of us is a normal human being. Outside the classroom, he to has his likes and dislikes like many of us. Therefore try to find out which coffee shop does he visit. You can buy him a gift certificate for the coffee shop. Chocolates are something, which many of us like. So does your teacher to. This is an ideal gift if you feel your pocket is a bit empty. Care should be taken to make the gift beautiful and should suit the occasion to the hilt. Sometimes simply gifting a card will do more wonders than giving him an expensive gift. You can simply write how much you love him and give it to him. I am sure he will like it as you are his student.
Flowers are another way of winning your teachers heart. You can probably go up to him with a beautiful set of roses and I am sure he will welcome you warmly. A teacher gives more than he gets. While few of you may grumble about the fees you have to pay, the knowledge he imparts upon you is great. You will realize it in the later stages of your life when your education will help you to stand up and face the world with courage.