Participants grades will be obtained in both assessments points. Individual and sum of disciplines grades changes will be considered to comparisons purposes.

Information about self-perception of physical and mental health, academic performance, behaviors (exercise and sleep habits) and social relationship will be assessed by a specific questionnaire for the participants. In addition, the intervention group ones will report their expectations (before) and perceptions (after) of the standing desks use.

Parents/guardians (individual level) and teachers perceptions (cluster level) about discipline, social interaction, academic performance and health behaviors of the children will be collected by a questionnaire filled before and after the intervention.

Considering the costs of classroom environmental adaptations and their effects on primary and secondary outcomes, the incremental cost-effectiveness ratio will be calculated comparing with costs of a traditional classroom.

Visual-spatial working memory capacity will be assessed through Coop Corsi block-tapping test. A 3 × 3 grid of 9 blocks indicates a spatial sequence by changing the colour of one block at a time, and participants were then asked to repeat that sequence by clicking on the blocks in the same order. During the 12 trials, sequence length increased by 1 block location each time the participant correctly repeated the sequence. Any error in repeating a sequence led to the next sequence being shortened by one location. The variable of interest was mean memory span, calculated as the average length of the three longest correctly repeated sequences.

Sensitivity to interference and the ability to suppress an automated response will be assessed using the Stroop color test. The Stroop test consists in two levels. Both levels involve the test word being placed in the center of the screen, with the target and distractor presented randomly on the right or left of the test word. The target position was counterbalanced for the left and right side within each test level. The participant is asked to respond as quickly as possible, using the left and right arrow keys, to identify the position of the target word. The variable of interest is the proportion of correct responses made.

Sustained attention and visual scanning ability will be assessed using the d2 test. This paper-and-pencil task requires participants to detect "d" symbols with two dashes (that may be located either both above, both below, or one above and one below the "d") among distractors ("d's" with one, three, or four marks or "p's" with one or two marks).

The concentration performance score was determined on the number of correct responses minus errors. Higher scores indicate a better and more stable performance.

Neuropsychological assessment will be assessed using the Raven's Progressive Matrices. The test provides a simplified 36-item paper format. Each item contains a pattern problem with one part removed and six pictured inserts of which one contains the correct pattern. Participants point to the pattern piece they select or to its number. The total score is the total number of matrices completed correctly, and the test is thus scored out of 36.

Neuropsychological assessment will be assessed using the Rey-Osterrieth complex figure test. The Rey-Osterrieth complex figure test (ROCF) is a neuropsychological assessment in which participants are asked to reproduce a complicated line drawing, first by copying it freehand (direct), and then drawing from memory (delayed copying). ROCF includes 18 units and the maximum score for each of the two tasks (direct and delayed copying) is 36. Two points are given when the element is correctly reproduced, 1 point when the reproduction is distorted, incomplete but placed properly, or complete but placed poorly; 0.5 point is credited when the element is distorted or incomplete and placed poorly. A zero score is given when the unit is absent or not recognizable.