Here are some external sites that students have found useful for supplementing and enriching their music education.
musictheory.net
Introductory and intermediate music theory lessons, exercises, ear trainers, and calculators.
Practice Sight Reading and Sight Singing Exercises Online – Sight Reading Factory®
SightReadingFactory.com makes practicing the important skill of sight reading quick, easy, effective and fun! This cloud-based service allows you to customize and generate unlimited sight reading examples instantly, on-demand for students of all ages and abilities.
Maryland Music Educators Association
The Maryland Music Educators Association is a leading advocate for music education encompassing a broad range of cultural and musical experiences and the right of every student to experience the power of music. MMEA is a registered 501(c)(3) non-for-profit organization.
National Association for Music Education (NAfME)
NAfME, among the world’s largest arts education organizations, is the only association that addresses all aspects of music education.