If a student graduates with a Bachelor majoring in IT, is it ok to continue with a Master and a PhD?
It depends, for example if we follow the ACM standard of what is an IT career you will find that it is oriented, mostly, to the technical part and not so much on the theoretical part of technology. In case, that you would want to attract students for pursuing higher academic careers in the IT field, you will have to include theoretical courses considering the computing curricula of ACM in the field of Computer Science.
The part that you mentioned that an IT graduate is to get quickly into the job market is true. They do not need to know the caveats of the theoretical foundations of CS, but they do have to know which TI tools are "hot" in the market and how they have changed from previous version.

In some parts of the world the IT term refers to any career related to technology, so that it could comprise also fields such as CS or SE, so it the students have followed these foundations they can go to higher degrees.

Personally, I have some colleagues that came from pure IT careers and then pursue a MSc in CS and for being honest; they passed thru very hard times, because they lack the knowledge of specific parts needed for their masters such as Algorithms, Advanced Data Structures, etc; also they needed to show proficiency in at least one programming language, but they lack that also.

Hope you find this information useful.