Number of students, bubble groups and SARS-CoV-2 infections by grade in Catalan schools (including preschool and primary grades)
| School year | Mean age (SD) | Students (n) | Bubble groups | Cases from 13 September to 22 December 2021 | Index cases (outbreaks) | Secondary cases | % of outbreaks without secondary cases |
| P3 | 3.1 (0.3) | 54 210 | 2932 | 942 | 724 | 307 | 75.3 |
| P4 | 4.0 (0.2) | 60 094 | 2994 | 1388 | 976 | 526 | 72.7 |
| P5 | 5.0 (0.3) | 63 344 | 3040 | 1966 | 1133 | 1052 | 64.2 |
| 1 | 6.0 (0.2) | 66 204 | 3148 | 2346 | 1405 | 1269 | 61.3 |
| 2 | 7.0 (0.2) | 67 455 | 3186 | 2781 | 1569 | 1566 | 56.3 |
| 3 | 8.1 (0.3) | 66 614 | 3131 | 3074 | 1638 | 1877 | 53.1 |
| 4 | 9.0 (0.3) | 71 590 | 3292 | 3703 | 1879 | 2436 | 52.6 |
| 5 | 10.1 (0.3) | 73 702 | 3349 | 4062 | 2029 | 2611 | 51.0 |
| 6 | 11.0 (0.3) | 76 101 | 3503 | 4500 | 2051 | 3092 | 48.8 |
| Preschool education (P3–P5) | 177 648 | 8966 | 4296 | 2833 | 1885 | 70.0 | |
| Primary education (years 1–6) | 421 666 | 19 609 | 20 466 | 10 571 | 12 851 | 53.3 | |
| Total | 599 314 | 28 575 | 24 762 | 13 404 | 14 736 | 56.8 | |