A classroom, schoolroom or lecture room is a learning space in which both children and adults learn. Classrooms are found in educational institutions of all kinds, ranging from preschools to universities, and may also be found in other places where education or training is provided, such as corporations and religious and humanitarian organizations. The classroom provides a space where learning can take place uninterrupted by outside distractions.

In elementary schools (from Kindergarten through 5th grade), classrooms can have a whole group of 18 to 30 students (in some cases these numbers may differ) and one, two, or even three teachers. When there are two teachers in a classroom, one is the lead teacher and the other one is the assistant teacher. Or the second teacher might be a special education teacher. There may be a third teacher in the back watching and taking notes. In lower elementary the classrooms are set up slightly different from upper elementary. In these classrooms there are tables instead of desks, a rug with a (Smart Board) for whole group learning, a library, computers, and centers. The rug is the focal point of the classroom and everything else is strategically placed around it. The teacher must be able to move swiftly through the classroom. To determine if the classroom is meeting the highest level of quality there is a grading scale called ECERS (Early Childhood Environment Rating Scale). There are 43 items on this checklist and it is divided into seven categories and they are as follows: Space and Furnishings, Personal Care Routines, Language-Reasoning, Activities, Interactions, Program Structure, and Parents and Staff. In an upper elementary classroom students now use desks, there is no rug for whole group learning but there is a Smart Board and computers. Students also start practicing switching classes to get accustomed to middle and high, usually in fifth grade school transitions.

In a self-contained classrooms there are 7 or fewer students. Self-contained classrooms are designed for children that need more one-on-one time. Teachers get to solely focus on their small group of students and create individualized lessons for each child. An integrated or inclusion classroom can be thought of as a mix between a traditional classroom and a self-contained classroom. In this style of classroom, there is a mix of general students and students that need services. There are two teachers in this style of classroom, a general education teacher and special education teacher. They both teach and serve the students in the classroom, but during certain parts of the day the special education teacher may pull the students that have services to give them additional support. This allows students with accommodations or an Individual Education Program (IEP), to still get to be in a general classroom but also get the individualized instruction they need.

Middle school and high school classrooms are set up quite similar. There is one teacher and students transition from one classroom to the next. They do not stay in one classroom all day. These classrooms can have around 20 students. Students may not exactly have the same group of students in each class depending on the students' schedules.

Then college classrooms are set up in a lecture hall or auditorium with one teacher, also called a professor. Typically this teacher has a Teacher Assistant (TA), which is a grad student. This person may help administer or grade tests. They can also hold review sessions for college students to come to once or twice a week.

Some other types of classrooms that a middle/high school or college might have include computer labs for IT lessons, gymnasiums for sports, and science laboratories for biology, chemistry and physics.

The layout, design and decor of the classroom has a significant effect upon the quality of the educational experience. Attention to the acoustics and colour scheme may reduce distractions and aid concentration. The lighting and furniture likewise influence factors such as student attention span.

Historically, relatively few pupil-centric design principles were used in the construction of classrooms. In 19th century Britain, one of the few common considerations was to try and orient new buildings so the class windows faced north as much as possible, while avoiding west or southern facing windows, as in Britain northern light causes less glare. Desks were often arranged in columns and rows, with a teacher's desk at the front, where she/he would stand and lecture the class. Little colors were used to avoid distracting the children. In the 1950s and 60s, cheap and harsh fluorescent lights were sometimes used, which could cause eyestrain. Research has suggested that optimal use of daylight, acoustics, color selection and even the arrangement of the furniture in the classroom can affect pupils' academic success. Georgetown University found that test scores increased by 11% through the improvement of a classroom's physical environment.