Teachers get to school early in the morning to prepare for the day. Help fuel their systems by providing breakfast for them. You can make this an ongoing project all year by providing breakfast once a week, or simply do it every day during Teacher Appreciation Week. Donuts and coffee in the break room are nice, or provide a muffin on each teacher's desk. Further personalize it by giving them a coffee mug with their name on it the first day you provide breakfast. This is a keepsake they will cherish for many years.
Make up a container full of candy or other treats for the teacher. A simple container or bucket works well. Decorate it using paint pens or paper to further dress it up and personalize it. Fill it with a candy or treat you know he will enjoy.
This project takes some time, so plan ahead. Give each child a square of fabric and have her decorate it with her name and something special about herself. Make a large square dedicated to the teacher; include her name, the school year and the grade she teaches. Gather all the squares from the students and sew them together into a classroom quilt. Present the quilt during Teacher Appreciation Week or at the end of the school year. This is an item the teacher will get good use out of.
You don't have to have a big project to show the teacher how much you appreciate her hard work. Simply write your heartfelt thanks in a small note. She will also enjoy a small bouquet of flowers on her desk or at home. Even a picture drawn by a small child is sure to please her, because if was drawn for her.