One seifuku a year, or several?

I know it's a crazy question, but I was thinking about how many gakurans the average student owns in Japan. I'm about to buy myself one of those gakurans to wear to school, but I'm thinking about buying more. It sounds logic... But getting one seifuku each year, providing you go to the next class after the end of each year... So you use the same seifuku year-round until advancing? Anyone an answer?

When I went to school in Japan from elementary (shogakko), middle school (Chugakko) and high school (Kooko), I usually had at least two every time. I did not change every year as long as they can still fit. But I remember having at least two and maybe three.

Chad

I'm a parent, and most students buy only one (for one school). It's not that cheap, you know. But most schools today do not have gakuran uniforms.