Hi, hopefully some violin teachers or musical mums will be along to help, but I can try and start from a non-musical mother with a 12 yr old DD (Y7) who plays the violin at a reasonable level.
However, first of all, how old is your child? He/she enjoying music at school? Is your child learning 121 or in a group? Any access to orchestras/ensembles? Has your child developed good sight reading, intonation and technique with the teacher? Do they play scales, studies as well as pieces? Sorry, not very familiar with Suzuki method...
Lots of questions - just not sure what your objectives are, and comparing against other children (or YouTube!) can be unrealistic as all have different learning styles.
Grades are an odd thing, but I guess is the uniform way people can gauge the level of your child. We've come up the ABRSM way, doing most but missing a few. She's not done an exam since Easter Y5 but would be comfortably G8 level now. Exams were done religiously up to then to secure a music scholarship...call it box ticking.
However, if we had our time again, we would not have done things this way. In the last 18 months, she's had to go back to some basics, widen her repertoire, lots of technical studies etc. It's relatively easy to learn a piece (yes, even Bach Double) but playing them well is different. As the pieces get more complex, they need to understand the mood of the piece. Teaching a 10 year old to play Schindler's List but doesn't understand the history is tough thing to do, but wow, can it change once they understand what was behind the piece/composer's viewpoint.
Look at the wider exposure your child has to music, are the basics being covered (e.g. do they make a good sound...basic I know but honestly, not all do) because getting these elements right can make them fly later.
Mine has a lot of music experience via orchestras, quartet ensembles etc and attends residential music schools since 9, in addition to school stuff. This is what stretches her, not the 3 pieces learned to rote for a hoop to jump. Exams have been a necessary evil for her to be judged for school entry, but thankfully is not required for junior music colleges/conservatoires etc if that's where your child wants to progress. State schools that offer music scholarships tend to work on aptitude tests, so again grades not necessary.
Lots of really helpful people/teachers on the MN extra curricular music threads, where there's some exceptional children talent, but also lots of help to get through the tough music times.
Sorry, long answer (and tired) but hope it helps...