Imagine it's your child's first day of kindergarten, and you anxiously drop her off at school. You're proud that she's achieving this milestone but also worried that she won't fit in, won't find her voice within the class. Would you rather her first real experience with school be in a classroom with one teacher, one aide, and 30 students, where the adults are frantically running around spending all of their time trying to corral the students and maintain order, or in a classroom with one teacher, one aide, and 18 students, where each student gets all of the attention they need? Or for your child who is just going off to high school, entering those essential years to prepare for college, would you want him to be in a lecture hall with 50 other students? Or would you want him in a class with 15 others, where the professor had time to answer every student's questions? Schools with small class sizes are more successful overall in terms of helping students meet educational benchmarks, and are especially successful at helping underprivileged students meet those benchmarks.
Reducing class size confers a wide variety of advantages, the most simple of which is time. Fewer students means on average fewer discipline problems as well as less time spent ensuring the entire class is on track. It also means fewer students that need individual attention. This gives teachers more time to dedicate to the students that do need help with the coursework. Where in a large class, students that don't understand a concept might be forced to see the teacher outside of class (reducing the amount of time they have to do homework or participate in extracurricular activities), in a small class the teacher often has time to help the student during class. This extra time also provides teachers with the ability to delve a bit more deeply into subjects that the class finds particularly interesting without risking falling behind.
Another benefit to reducing class size is the corresponding reduction of distractions. The fewer students in a class, the easier it is to deal with those students who do cause trouble and the less likely a discipline issue is to spiral out of control. Not only are teachers less busy "putting out fires" in terms of maintaining discipline, but students can focus better with less frequent distractions from their peers. So students' questions get noticed and addressed more reliably, but they also have fewer questions in the first place because the smaller class size helps them stay focused for longer periods of time.
Reducing class size does not come without its difficulties, however. The difficulty of the most concern to schools and school districts is cost: smaller class sizes means more teachers, which means more salaries that the district has to pay each year. Because so many schools struggle with funding as is, the thought of increasing spending at all can be terrifying. There are a few ways around these financial woes, however. First of all, because state funding is connected to an extent to student performance, the improved education that students receive can help soften the blow of hiring more teachers. In addition, while strictly public schools have slim margins regarding funding, many charter and private schools possess a bit more leeway as far as money is concerned, so they can afford to hire enough teachers in order to keep their class sizes small.
Overall, if reducing class sizes is financially feasible for a school or district, it is one of the best ways to improve the quality of education that school provides. Smaller classes tend to help academically challenged students more than academically gifted students because academically gifted students rarely need a large portion of the teacher's attention anyway, freeing the teacher to focus on the students that actually need help. This greatly improves the class' performance and gives the students the tools they need to be successful in higher education and beyond.