Objectives: After categorizing preschool children into "active and low active" according to their moderate and vigorous physical activity (MVPA) in PE classes (PE), we compared these two groups within each sex and by sex in: (a) % MVPA and MVPA minutes accrued from each fundamental motor skill (FMS) during PE and (b) % MVPA during school time. Results: 532 children (mean age 5.2 years, 50% girls) were selected from a nationwide program which provides 3 weekly PE. Children wore accelerometers during one school day which included PE. We recorded the type and duration of each activity indicated by the teacher, classifying each one into the corresponding FMS, extracting its MVPA minutes from the accelerometer software. Children were categorized into active and low active. Comparisons used T-tests. In PE, active children accumulate 40 and 36 percentage points (pp) more MVPA minutes (boys and girls respectively), while during school time, 4 pp more in each sex. Girls are significantly less active. Just considering locomotion, active boys and girls accumulate 11 more MVPA minutes during PE. Active boys surpass the MVPA guideline for PE, while active girls almost reach it. Low active children (especially girls) should intensify locomotor activities during PE.