whats the highest level of education i need to become a graphic designer

Degrees are usually what we compare in different levels but for graphic design, it doesn't matter if you have an associate's or bachelor's or master's. Obviously, if you have master's, you should be considered above than associate's or bachelor's. Master's is the highest level of education but it doesn't make you in the high level in graphic design.

Most jobs require experience so the best way to get higher level is doing a job and making your designs better. If you're still in school, look for internship, it will get you real-world experience.

Try doing freelance work too, it might give you a direction where you're at in the designing level.

I know qualified graphic designers with Associate's degree (2 years) and Bachelors degrees (4 years). If the program you get into has a good internship placement requirement (which is something you want to ask before deciding to enroll!), then you may be trained to work at a particular company, and more likely to get a full time job there after you graduate.
For job-security reasons a lot of graphic designers get their Bachelors because it looks more attractive, but I've seen designers who run their own business who are self-taught (meaning they didn't go to school for design training). Those folks usually have a harder time getting a job in a firm however.

The question should be "what is the lowest level" as one doesn't need the highest level. Or maybe "what is the highest level one can get" (but not needs).

The lowest degree level is associates, but it even isn't necessary for one to be a graphic designer. The highest is maybe a Masters degree, but it's generally considered needed only for teaching at a University or maybe for a competitive edge.

If one's looking to get hired on as a full-time designer, the minimum requirement will be decided already and there may not be a lot of leeway there unless it's a small firm as larger companies have HR departments that often weed out resumes by the stated requirements. This is also where the competitive edge comes in. The stated requirement may actually be low if there are other candidates out there with a higher education level willing to take a job. Or it could turn out to be higher than what they end actually willing to hire for if there aren't candidates. That's something that fluctuates depending on economic conditions and with how desirable a company or job is at the time.