I was hoping to use donated retired smartphones as tablet type devices for my students. I'm interested in accessing apps, taking pictures, that kind of stuff. My school has wifi.
Welcome to the forums. Yup, devices without service can be used on wifi only. Easiest way to do it is to put the device in airplane mode (to kill any accidental use of the cell radios; Don't need emergency calls being made in class), and then activating the wifi radio.