I have a list of SObjects Ed, each SObject SEH is a detail to a Master SObject Student. Each Master SObject Student has a lookup field to SObject Cohort that may be null.
If it the lookup field is not null I want to record Cohort.Name, indexed by that Student. Also I want the list to be unique as multiple Ed entries may point to the same Student.

This is in a trigger so I want to do one SOQL query to create a map to use inside my main for loop. What I'm thinking is that if I can create a list (say studentList) of the Master Object (Student) Ids, I can do a single map statement that will fill from [Select Id, Cohort__c.Name From Student Where Id in :studentList]. It seems like there should be a simple way to create List<Student> studentList... directly from the list of Ed.

Best I have so far is
        map<Id, Boolean> studentMap = new map<Id, Boolean>();
        List<Id> studentList = new List<Id>();
        for (Ed__c stu : edHists) {
            if (stu.Student__c != NULL) {
                if (studentMap.get(stu.Student__c) == NULL) {
                    studentMap.put(stu.Student__c, TRUE);
                    studentList.add(stu.Student__c);
                }
            }
        }
      
        map<Id, Student> studentCohortMap = new map<Id, Student>([
            Select Id, Student__r.Name
            From Student
            Where Id in :studentList AND Cohort__c != NULL
        ]);

Is there something more efficient and/or simpler that my Friday afternoon brain is just missing?