What’s your reference point? Co-ed means a school with both males and females; unisex….are you using this to mean a school that accepts only one of the two genders? If so, find a different word to use once you decide upon your thesis sentence. Sounds like a Freshman Comp class essay assignment. If so, your thesis should state your position (and be the last sentence in the first paragraph); the body of your essay (minimally 3-5 paragraphs long)should provide support for your position (reasons why); the conclusion should summarize your essay from the particulars to a generalization.

that totally depends on the situation. most of life nowadays is co-ed though.