Most simply, but anyway good style:
Das ist der Student, den ich unterrichten soll.
Depending on context and preliminary knowledge of circumstances it can also be sufficient and appropriate to say:
Das ist mein Student.
In a very formal setting you may also say
Das ist der Student, der mir für den Unterricht zugeteilt wurde.
Das ist der Student, der mir für den Unterricht zugewiesen wurde.
But I can hardly imagine a real-life situation where such a bureaucratic way of speaking would be appropriate, except perhaps in a formal letter to the head of the university if you do not know him/her personally yet. (Or, theoretically, in a parliamentary debate.)
More simply, this is also a good sentence:
Das ist der Student, der mir zugeteilt wurde.
as long as it is clear from context that the assigment relates to being taught, not to other things such as being asked to do a job or whatever which then should be mentioned explicitely as in:
Das ist der Student, der mir zur Krankenpflege zugewiesen wurde.
Please note that Student always refers to a student in higher education. If you want to address people learning at school (secondary education or lower) you would call them Schüler.