I met people who get into playing very few pieces and ignore other composers or other pieces by the same composer than the ones they like. Teachers would assign pieces with different styles & by different composers. Some you would like more than others. Playing a variety of pieces is part of the process when you're taking music lessons. Some teachers would organize year-end concerts for students to showcase their playing to the parents. They can pick only the pieces they like.
Some composers like Bach, Handel, Mozart, Chopin, Liszt wrote many pieces for the piano. Other composers wrote for the orchestra & other instruments but not for piano. If you want to focus on specific composers like Shostakovich and Prokofiev, you can go to Wikipedia and get a listing of their works. To find a specific piece in a piano version, you'd go to a site like Sheet Music Plus
and try your luck under the piano section. Many of the pieces comes in arrangements in different keys from easy to advanced.
I'm with a teacher and the books I used before her summer break below including a number of books from the Faber series you might like. The PlayTime Piano Classics Level 1 may be too basic for your student. The BigTime Piano Classics Level 4 I'm using may be the right book. The book has a variety of easy pieces arranged for piano including Massenet "Meditation", Fauré "Sicilienne", Chopin "Ballade" and others. Each piece is in large print and no more than 3 pages. The BigTime Jazz & Blues also from Faber is at the same level.
"First Lessons in Bach" is a book with a number of easier pieces from the "Notebook for Anna M" and by the composer. Here is a book with I & II together. You can buy them separately. Of course book I is easier. If you're into Bach, this is the book for you.