For undergraduate-level composers especially, a long list of compositions is more impressive than a short list, so you should not worry about including earlier works you may now consider juvenile. Chances are, whoever is reading your resume will only see the compositions you submit anyway. For performers, include other instruments for which you have some level of proficiency. Include years studied. This category is an alternative that may be redundant for those who include their summer camp experiences under the Education section.
Some musicians prefer to make a distinction - either way is fine.