A diagnostic assessment is a short test that shows a teacher what each child has and has not learned, so that the teacher can teach the missing parts again. It is used to find gaps, not to pass or fail a child. It is a part of an adaptive learning platform, and it is often run at the start of a school year or a new topic.
How is it different from an exam? An exam measures how much a child has learned at the end, and gives a mark. A diagnostic test is built to explain the mark. Each question tests one skill. The wrong options are chosen with care, so that each wrong option matches a particular mistaken idea. So the teacher learns not only that a child got a question wrong, but also why.
Surveys of Indian schools have found for years that many children are one or more classes behind in reading and maths. A teacher of 40 children cannot sit with each child to find out where that child is stuck. A diagnostic test does this for the whole class in 30 minutes.
Here is a typical case. A Class 4 maths teacher at a school in Bhubaneswar gives her 30 students a 20-question diagnostic test on a tablet in the computer lab. The questions cover place value, addition, multiplication and simple fractions. The results arrive the same afternoon. 26 of the 30 children can add two three-digit numbers. But only 9 of the 30 can say which is larger, one-third or one-quarter. 14 children chose one-quarter. They think that a fraction with a bigger number below the line is a bigger fraction, because 4 is larger than 3.
The teacher now knows exactly what to teach. She spends the next week on fractions, with paper strips that the children fold into thirds and quarters, and she skips the addition revision that she had planned. After the week, a short retest on fractions shows that 22 of the 30 children now answer correctly. The 8 who still struggle get extra practice on the adaptive platform, which uses the diagnostic results to choose their questions.
Designing such tests is a specialist job. The test makers try each question on many children first. They keep a question only if it separates children who know the skill from children who do not, and they drop questions that confuse everyone. The same science of measuring ability with tests, called psychometrics, is used in pre-employment assessments that companies give job applicants.
The results can also be sent to the school's learning management system (LMS), so that the teacher can assign the right practice to each group. Some newer products add an AI tutor that talks a child through the skill that the test showed as missing. The general idea behind choosing the next question from the last answers is explained in adaptive learning.