This “competitor” to GarageBand (only in a sense as it is also under the Apple umbrella) is certainly a superior and more complete program for music composition and engineering, though it is not free. In addition, because it is more robust, it is also more complex as it has more offerings in the intricacy of sound production.
While this app wouldn’t replace an actual amp for playing a show, it is a quality substitute for amplifying when practicing on the go. It does cost money (and is on the pricier side for apps), but it could be worth having on an iPad in the music department, and worth mentioning to serious student musicians who may make good use out of it at home.
Hokusai is a quality recording app for student artists who play actual instruments rather than create using virtual ones. You can blend different parts of a musical piece together and because it quickly digitizes your music, you can dig in like a sound engineer would.
GarageBand is still one of the leaders in music education, primarily because students need not play an instrument to begin making music. The ease with which you can transition between other multimedia platforms (particularly iMovie) makes it a “go-to” for project-based learning, even outside of music education. While you may be familiar with earlier versions, it is worth checking in each school year to explore the ever-growing features and enhancements, most notably with how different young student musicians from around the globe can collaborate in real time.
Apple teamed up with Pharrell Williams to create Tuniversity. It is a robust program that allows students to deconstruct popular songs, change them up, and write their own. It is powered by Garageband, but also contains an interactive digital syllabus that takes students through their coursework.
Yousician is a great way to engage students in practicing their instrument, outside of lesson time. There are dozens of instruments and thousands of songs to dive into. It tracks progress and personalizes a syllabus that is constantly updating. You may also want to check out the added benefits of becoming a Yousician Distinguished Educator.