If you read all the similar posts, you will see that teachers don't want individual gifts that say #1 Teacher or that they will feel obligated to display on their desks. 22 kids a year (maybe fewer in pre-K) x 2 gifts a year x 15 years of teaching = too many things that go into yard sales! Same for baked goods.
If you know the teacher well and know her tastes, you can go for nice coffee or wine or chocolates BUT be cautious because if they get 5 tons of this, it goes to waste. Same goes for things like mani/pedi or boutique gift certificates - you have to be sure the teacher likes that.
Many teachers use their own money to buy school supplies not covered by the budget, so office supply and teacher supply stores are good for gift certificates.
Our schools have done 2 things. One is, we organize the parents and collect money from any who wish to participate. People give what they can afford based on their circumstances and the number of kids they have (4 kids means a lot of teachers), and then a group gift is purchased. This can be one big gift card or a basket with a variety of things. The other thing we have is an Educational Foundation to which parents and grandparents and anyone in the community can contribute. The teacher gets a note from the foundation that a donation has been made in her honor by Johnny Smith and family. Then any teacher can apply for a grant from the foundation to implement a program or curriculum addition that is not covered by the budget. This does a lot of things - it puts the money back into the classroom, and it allows ANY teacher to apply. That means that phys ed and music and art teachers can apply for funding, and parents don't have to worry about trying to buy for every teacher who touches their child's life.
If you are in a private pre-K, that foundation idea won't work, but it will if it's a pre-K class in the public schools, as well as going forward.
So for private pre-K, you can also get a gift card for any place that has a variety of gift options. Could be a coffee place that has sandwiches etc., or it could be a department store. I try to support local businesses so I often give a gift card to a small place where she can either buy for herself or buy a gift for someone else that she would have to shell out her own money for. I would say NOT to give a restaurant gift card because the teacher will always have to top that off with her own money - $25 is a generous gift from you, but she and her husband or friend cannot get a full meal for $25, you know?
And put in a note from your child - have the child dictate it so it's REALLY from the kid, and it will make the teacher smile!