There are three levels of awards (in ascending order): the bronze and silver certificates and the most prestigious Green Flag. Each award is defined by a set of criteria (available both in Maltese and in English) that help you decide whether your school has achieved the required standard. If you feel that your school has met most of the required criteria for a particular award, then you should seriously consider applying for that award.
In your quest for the Green Flag, you do not need to go through the bronze and silver levels. If you think that your school has achieved Green Flag standard than you should apply for that level directly. When you apply for a Green Flag, the evaluators are not after environmental perfection. The most important element in the EkoSkola programme is its emphasis on continuous school improvement stressing the process rather than the products.