Is it plugged into an active electrical socket? Sometimes there is a switch on the wall that turns the electric socket on/off. Make sure that switch is turned on.
Does the charger have a good connection? Make sure the charger cord is firmly attached and the LED light is on. The newest Chromebooks have a C-USB connector on either side of the Chromebook. If you have a Chromebook with that option and one side is not charging, try the other side.
Is there an amber light on while it is plugged in and charging? If there is no light, the battery is completely drained. When that happens, the Chromebook will not turn on, even if it is charging. Let it charge in an active electrical outlet for 15 minutes. If no light appears you may have other issues, contact the technical support by submitting a service request form on our school website.