The District phone system connects all campuses. To call anyone in the District, just dial their 4-digit extension, even if they work at a different site than you. Phone extensions are listed in the staff directory (access via the TUHSD Portal), and also in the on-phone directory.
Office extensions can be called directly from outside the District; classroom phones cannot be reached directly by outside callers. Outside callers can call the main number of the campus, and then be transferred to classroom phones. Classroom phones do NOT ring during school hours for outside calls; those calls are sent directly to voicemail.