Is it considered unjust to count a student as absent for the first class period if they are 15 minutes late, despite their presence for the remaining 30 minutes? Will the teacher be held accountable for this, and is it permissible for them to violate the rules if such a rule is unfair to the student?

If the system prevents the latecomer from entering or considers him absent, there is no objection to that, and it is not an equalization between the absent and the latecomer. Rather, it is an encouragement to adhere to time, while allowing the latecomer to attend the remainder of the class to benefit, whereas they could have prevented him. Those in charge of education are permitted to establish regulations that serve the students' best interests, and the teacher must adhere to them unless they contain something forbidden.