You typically use an indexer if the class represents a list, collection or array of objects. In your case, you could provide an indexer to provide index-based access to a teacher's students. You would use an enumerator if your data is normally accessed sequentially.

What are indexers used for?

Indexers are a syntactic convenience that enable you to create a class, struct, or interface that client applications can access as an array. The compiler will generate an Item property (or an alternatively named property if IndexerNameAttribute is present), and the appropriate accessor methods.

What is indexer and use of it?

An indexer allows an instance of a class or struct to be indexed as an array. ... Array access operator i.e ([ ]) is used to access the instance of the class which uses an indexer. A user can retrieve or set the indexed value without pointing an instance or a type member. Indexers are almost similar to the Properties.