Class sizes in high school should be smaller

This is a persuasive essay in MLA format. I am having trouble making the essay flow. Also, my thesis statement is not quite good enough. The length is OK, it can be between 800 and 1000 words. My transitions are also poor. I can not seem to get from one paragraph to another smoothly. Any help with wording etc would be appreciated. It needs to be in present tense.