You need to review the definition and concept of an ATC clearance. This is what a lot of of student pilots are taught by their instructors. This wrong interpretation has been passed on to pilots over and over. (Don't mean to throw you under the bus) Why? Because a lot of pilots can't tell the difference between an ATC clearance and two way radio communication. So to be on the safe side, flight instructors tell their student to ask and hear the words "Clear into Class B". This is why ATC yells at pilots when they received a heading and altitude assignment and still ask if they are clear into class B!!! And yes, I do enter in class B ALL THE TIME without asking or hearing "Clear into class B". What is the difference? In most case I do get a more professional and expeditious service from ATC because they know who they are dealing with.

This being said, you are RIGHT also. If ATC doesn't care where you are going and just wants you to proceed VFR, this is not in this case an ATC clearance. So you need to hear the words "Clear into Class B or something similar to that effect".

Let me ask you. If you received a heading and altitude assignment and then the radio becomes cluttered. Are you going to deviate from this "ATC clearance" because you didn't hear "Clear into Class B" and you are just about to enter class B? I hope not. And this is exactly what may happen to your students - an FAR violation. You think you do them a favor and this might bite them in the a$% later on. Let me ask you another question, you are departing from an uncontrolled airport for an IFR-IMC flight which requires you to obtain a clearance before entering controlled airspace, do you hear in any of that "Clear into class E"? I bet you never did in a million.