There is an unfortunate stereotype that Suzuki students can only learn by ear, and don't learn to read music. It isn't true, of course. Conscientious Suzuki teachers make reading an important priority, but they work on it at the appropriate time.
We would not think of teaching a child to read before he has learned to speak (except in rare cases). First we have to establish the foundation of linguistic concepts (vocabulary, pronunciation etc.), and only later (usually much later) is a child ready to comprehend the abstract system of symbols that we use to notate language on the page.
The same is true for music. Students who learn by ear first, and then learn to read, can develop a comprehensive knowledge of how to interpret the symbols on the page and translate them to musical sounds. Students who only learn music by reading often miss a lot of information. They have trouble seeing on the page where one phrase ends and another begins. Their sense of pulse is often mechanical and conceptual rather than intuitive, and the result is very stilted. They have to process each instruction on the page individually. They also have a much harder time memorizing.
Suzuki students do start to learn to read when the time is right. That time depends on a lot of factors (age, security of posture and set-up, aural development etc.), and varies from student to student. When I start students reading, I use material outside of the core Suzuki repertoire, so that I can be sure that they are in fact learning to read, rather than reading by ear. In the meantime, I introduce pre-reading concepts essentially from the start, much the way young kids learn the alphabet long before they are actually reading.