How to make a call from your classroom phone to an extension in the school system...
Pick up the handset, type the extension, and then press the button located below 'Dial" on the screen to talk through the handset.
Press the speaker button on the front of the phone, type in the extension, then press the button located below 'Dial' on the screen to speak on speaker phone.
Type in the extension and then just pick up the receiver.
How to dial an outside number from your classroom phone...
Use one of the methods above.
You do not have to dial anything special to dial out. Simply dial the 10 digit number. For example 7066574367.