One of the most influential articles ever published in the field of educational psychology was a paper by John Carroll titled "A Model of School Learning" (1963, 1989). In it he describes teaching in terms of the management of time, resources, and activities to ensure student learning. Carroll proposed that learning is a function of (1) time actually spent on learning and (2) time needed to learn. That is, learning is greater the more time students spend on learning in relation to the amount of time they need to learn. Time needed is a product of aptitude and ability to learn; time actually spent depends on clock time available for learning, quality of instruction, and student perseverance.

Slavin (1987d) described a model focusing on the alterable elements of Carroll's model, those that the teacher or school can directly change. it is called the QA1T model (quality, appropriateness, incentive, time) of effective instruction.

1. Quality of instruction: The degree to which presentation of information or skills helps students easily learn the material. Quality of instruction is largely a product of the quality of the curriculum and of the lesson presentation itself.
2. Appropriate levels of instruction: The degree to which the teacher makes sure that students are ready to learn a new lesson (that is, have the necessary skills and knowledge to learn it) but have not already learned the lesson. In other words, the level of instruction is appropriate when a lesson is neither too difficult nor too easy for students.
3. Incentive: The degree to which the teacher makes sure that students are motivated to work on instructional tasks and to learn the material being presented.
4. Time: The degree to which students are given enough time to learn the material being taught.

Accommodating instruction to student differences is one of the most fundamental problems of education and often leads to politically and emotionally charged policies. Many secondary schools allow students, in consultation with counselors, to choose the level of each class, perhaps changing levels if a course turns out to be too difficult or too easy. These strategies, which result in students' attending classes that are more or less homogeneous in performance level, are called between-class ability grouping.

Another common means of accommodating instruction to student differences in elementary schools is within-class ability grouping, as in the use of reading groups (Bluebirds, Redbirds, Yellowbirds) that divide students according to their reading performance.

Probably the most common means of dealing with instructionally important differences is to assign students to classes according to their abilities. This between-class ability grouping can take many forms. In high schools there might be college preparatory and general tracks that divide students on the basis of measured ability.

Despite the widespread use of between-class ability grouping, research on this strategy does not support its use. Researchers have found that although ability grouping might have slight benefits for students who are assigned to high-track classes, these benefits are balanced by losses for students who are assigned to low-track classes.

Untracking recommendations focus on having students in mixed-ability groups and holding them to high standards but providing many ways for them to reach those standards, including extra assistance for students who are having difficulties keeping up.

One form of regrouping for reading, the Joplin Plan, regroups students across grade lines. For example, a reading class at the fourth-grade, first-semester reading level may contain third-, fourth-, and fifth-graders. One major advantage of regrouping over all-day ability grouping is that in regrouping plans the students spend most of the day in a mixed-ability class.

A form of grouping that was popular in the 1960s and early 1970s that is returning in various forms today is nongraded organization, or cross-age grouping. Nongraded programs (or cross-age grouping programs) combine children of different ages in the same classes. Most often, students aged 5 to 7 or 6 to 8 maybe mixed in a nongraded primary program. Students work across age lines but are often flexibly grouped for some instruction according to their needs and performance levels.

Students of high, average, and low achievement levels seem to benefit equally from within-class ability grouping. The research suggests that small numbers of ability groups are better than large numbers. Smaller numbers of groups have the advantage of allowing more direct instruction from the teacher and using less seatwork time and transition time. The main point to be drawn from research on within-class ability grouping is not that it is desirable but that if some form of grouping is thought to be necessary, grouping within the class is preferable to grouping between classes.

Another approach to accommodate instruction is called mastery learning. The basic idea behind mastery learning is to make sure that all or almost all students have learned a particular skill to a pre-established level of mastery before moving on to the next skill. The problem inherent in any mastery learning strategy is how to provide the additional instructional time to students who need it. In some of the research on mastery learning, this additional instruction was given outside of regular class time, such as after school or during recess. Forms of mastery learning that require additional instructional time are not easily applicable to elementary or secondary education, in which amounts of time available are relatively fixed.

The problem of providing all students with appropriate levels of instruction could be completely solved if schools could simply assign each student his or her own teacher. Not surprisingly, studies of one adult-one student tutoring find substantial positive effects of tutoring on student achievement. One major reason for the effectiveness of tutoring is that the tutor can provide individualized instruction, tailoring instruction precisely to a student's needs.

Teachers have long found ways to informally accommodate the needs of different learners in heterogeneous classrooms. In peer tutoring, one student teaches another. There are two principal types of peer tutoring: cross-age tutoring, in which the tutor is several years older than the student being taught, and same-age peer tutoring, in which a student tutors a classmate.

One-to-one adult-to-child tutoring is one of the most effective instructional strategies known, and it essentially solves the problem of appropriate levels of instruction. The principal drawback to this method is its cost. However, it is often possible, on a small scale, to provide adult tutors for students who are having problems learning in the regular class setting.

The decreasing cost and increasing availability of microcomputers and other technologies in schools have led educators at all levels to become more interested in technology, particularly as a means of meeting students' diverse needs.

The computer can be quite effective in presenting ideas, using pictures or diagrams to reinforce concepts. For many students, the computer seems to have a motivating quality of its own so that they work longer and harder when using the computer than they would on comparable paper-and-pencil tasks.

There are several types of computer applications in the classroom including: Drill and practice, tutorial programs, instructional games, simulation software, word processing software, spreadsheets and databases, CD-ROM, hypertext/hypermedia/Videodisc/DVD, integrated learning systems, computer programming, internet.

Most reviews of research on the effects of computer-based instruction conclude that computer-based instruction has small to moderate-sized positive effects on achievement. CBI is often effective when it is used in addition to regular classroom instruction; it has smaller and less consistent achievement effects when it entirely replaces classroom instruction.

Educational programs for students who are at risk fall into three major categories: compensatory education, early intervention programs, and special. Traditionally, Title I and other compensatory education programs have overwhelmingly emphasized remediation. In more recent years (December, 2001), the U.S. Congress passed the NO CHILD LEFT BEHIND ACT. This ACT made every school more visibly accountable (school/district report cards) for the achievements of every student. Under this ACT, there are provisions for improving teacher quality, reading instruction, scientifically based practices, and holding school more and more accountable for individual student achievement. Although NCLB does not dictate to the States what curricula to use, there most definitely is a greater emphasis on accommodating instruction in American Schools in addition to the advancement of extra services and programs.