There is a set of national standards in music education which most teachers adhere to. There is also a subset of exactly what students should be able to do for each standard within different grade levels (K-4, 5-8, 9-12).
Standard #1 - Singing alone and with others, a varied repertoire of music. Students learn to sing with correct pitch, rhythm, tone quality, diction (pronunciation of words), posture, dynamics, phrasing, and interpretation. They memorize songs in different genres, and learn to sing both solo and choral parts (first in only two parts; eventually in as many as 8 or 9). Students learn some of this in general music, and some in choirs. In choirs, students also learn to follow conductors.
Standard #2 - Performing on instruments, alone and with others, a varied repertoire of music. Students learn to play with correct notes, rhythm, tempo, dynamics, pitch, tone quality, and more. They learn basic percussion instruments (such a xylophone or bells) in general music classes. They learn other instruments in band or orchestra, later, where they must also learn the skills necessary to perform well on these instruments (including bowing, phrasing, hand position, breathing, and more).
Standard #3 - Improvising melodies, variations, and accompaniments. Students in elementary school may be given certain notes and told to play them in any rhythmic pattern. They may be given groups of notes and told to organize the groups in any order. They may sing a made up song. At older levels, students may add in harmony to a melody, create a melody for a harmony, or make up "variations" on familiar songs using different rhythms.
Standard #4 - Composing and arranging music within specified guidelines. Students may be given lyrics and told to write a melody line to it. They may write a solo piece for their chosen instrument. They may be asked to create music to go with art work. Older students may be asked to write works for small or even large ensembles.
Standard #5 - Reading and notating music. Students must be able to read notes on the grand staff and potentially in tenor or alto clef as well. They should be able to read any meter (simple or compound) and all of the note values within each meter. They should be able to read the music on their instruments or using solfege or a similar system. Students should be able to write down rhythms and pitch patterns (either made-up ones or ones a teacher plays on an instrument). Students should know all key signatures and the scales the accompany them. They should also recognize musical markings related to tempo, dynamics, phrasing, etc.
Standard #6 - Listening to, analyzing, and describing music. Young students should be able to move with the music (march in tempo, move their hands up or down with dynamic or pitch changes), draw what they hear, and more. Students should also be able to identify what instrument is playing, and use appropriate terminology to describe what is happening (tempo or dynamic-wise) in the music. Older students should be able to understand the underlying harmony in the music and write down what chords are being played. They should also be able to describe the musical form.
Standard #7 - Evaluating music and music performances. Students should be able to explain their musical preferences using correct musical terminology. They should be able to adequately assess their or another musician's performance in relation to dynamics, tempo, tone quality, tone color, intonation, style, articulation, and other musical terms.
Standard #8 - Understanding relationships between music, the arts, and other disciplines outside the arts. Students should understand common terms between music and the other arts. They should know how music relates to non-arts subjects and should understand why the other subjects are important to music and vice versa.
Teachers include these musical standards in their classrooms beginning in a kindergarten general music class, and ending in 12th grade general, band, choral, or orchestral classes. Some schools also offer history or theory classes at the high school level, in order to cover some of these are more in depth.
