Did you know that band directors can often tell which students will drop out of band by looking at the quality and condition of the instruments that they're using? Why is that?
It's because an instrument that is difficult to play or won't perform properly is a huge discouragement to beginning musicians. Like anyone learning a new skill, a beginner can find it challenging to make the first sounds. The instrument used during the first few months of study is critical in determining the success or failure of a young musician.
Beginners are learning the basics of making the notes, so beginner trombones typically don't have the features to produce a high-quality tone. Beginner instruments are designed for early use and gratification for the student.
Beginner trombones have small bores (the inner diameter of the tubes) to make the instrument easier to play. A small-bore requires less air but also produces a smaller tone. Beginner trombones come with small to medium mouthpieces and rarely include any special features--they are very much basic instruments for getting started.
By the end of the first year of musical study, a student is already outgrowing their beginner instrument both physically and musically. A musician's instrument should grow with them. This means it's time to step up to a more advanced, higher-quality instrument that will complement their developing music skills.
You may be wondering, "How advanced of an instrument is needed at this stage of musical study?" Step-up trombones are available in three levels: intermediate, performer, and top-line.
Intermediate trombones should have slightly larger bores. As students develop stronger embouchures (the facial position when playing a mouthpiece) and lungs, they can fill a larger bore with air and create a fuller, more resonant sound. Many intermediate trombones come with F-attachments like the one pictured below. (a valve and tubing that extends the low register and allows the trombonist an alternate way to reach difficult slide positions) Intermediate trombones are popular in junior high and high school bands.
In addition to larger bores and F-attachments, performer trombones usually incorporate slightly larger one-piece bells, special annealing of the brass, and hand-hammering. As a result, they have very full, rich tones and allow the player to more easily control the dynamics. These models are appropriate for young musicians who take their music seriously.
Top-line trombones are almost always large bore with an F attachment and typically incorporate all of the manufacturer's best features. Music majors or professionals most often play top-line trombones, although others sometimes choose them too.
A step-up trombone, particularly a performer or top-line, should last through school and longer — with regular maintenance a trombonist should not have to buy another trombone.