Teachers – They love anything but a mug or plate is something they get very often so try avoid those. Instead try getting or making them something more personal. I know you may not have time to make it but try getting them a fake plant so they do not have to give it much care and they can look of it and think of you. If they are healthy and active try a gift card for a sports shop they love of a healthy cooking book. Finally for the teacher who gets stressed or frazzled try a teacher survival kit that you can find ideas for online.
Parents – Once again they will love anything but I have found in my years of experience of you make them a card and buy something that will either be able to share with you ( a box of chocs I recommend dairybox or lint chocolate ) or something they will get a lot of use our of ( a shirt, gloves and a hat or a giftcard )