May son is a music Ed major. Most kids applying to college as a music major (performance, music Ed, or music therapy) are going to audition on one instrument and acceptance into the major will be based on that audition, so being strong on that one instrument is pretty important. My son did audition on two instruments (voice and cello) and frankly that complicated the application, audition, acceptance, and scholarship process. He was determined so he did it anyway. He’s a choral music Ed major (he was awarded a choral scholarship) but he takes concentration level lessons on cello as well. It’s difficult to really fully pursue two different instruments at the college level because ensemble rehearsals will conflict, forcing a choice.
That said, it is helpful to have experience on more than one instrument as a music Ed major. Music Ed students have to study all the instruments (son is doing a voice concentration but has taken/will take strings, woodwinds, brass and percussion classes, focused on being able to teach each of these categories of instruments. Every music major at most if not all colleges will have to take piano classes and pass a piano proficiency exam, so a background in piano is really helpful, although not necessary.