Flight instructor monitoring his student in the pattern visually and with hand held VHF; notice the student land behind another aircraft and follow it to the ramp. No contact is made with ground control. Student had interpreted instruction from tower to follow aircraft on short final as clearance to follow it to the ramp.

Narrative

While observing my student piloting during student solo practice take-offs and landings; I was listening on a hand held radio and noticed two aircraft exiting Runway X at intersection 'E'. The first aircraft made his exit and received clearance to taxi ''E'; 'C' cross Runways YYL and YYR'; and my student made the same exit only to proceed and follow the aircraft in front of him with no noted dialog with ground. I believe the cause of this possible runway incursion to be a result of student pilot confusion - where my student may have mistaken the instruction 'Number 2; follow Cessna on short final' and he proceeded to do just that - following that Cessna all the way to the ramp. I have debriefed my student and we have reviewed the situation and the required calls that must be made at each holding point including careful listening to; and understanding traffic control instructions and who they are for. I have further noted this potential misunderstanding and will provide instruction to future pilots about similar events and scenarios.