First of all, try to find out the interests and hobbies of the teacher or what he or she wants to do during retirement. Depending on this you could plan you teacher retirement gifts. Interestingly, many teachers are into puzzles, cards, boards and number games as might sometimes be related with their teaching. So, get them one of these to keep them amused as always.
If possible, get scrapbooks singed by all the students of your class including a group photo. Also include hand written notes in appreciation of the long dedication service and you will see how much the teacher will be appreciative of this. And as the teacher is retiring, how about a movie pass to some of his or her favourite movies. This could just be one of the best ways to start enjoying a retirement. A family dinner voucher would be great too.
Gift baskets always make great gift items and it could just be the same as teacher retirement gifts too. You could just fill in with items that the teacher can relish from time to time or even sweets and chocolates. Good foods are always a sign of life and celebration; retirement is the beginning of a new life. So, a gift basket filled with great food will make one teacher retirement gift.