Current resuscitation guidelines endorse placing the unconscious and normally breathing victims in the recovery position (RP), but this technique might hinder breathing evaluation. To compare breathing evaluation and cardiac arrest detection: placing the victim in RP and checking breathing regularly, placing the victim in RP while re-evaluating breathing every minute, and placing the victim on his back, maintaining an open airway with the head-tilt-chin-lift technique and continuously checking breathing. Schoolchildren aged 10–12 with no previous cardiopulmonary resuscitation (CPR) training, from three different primary schools were randomly allocated into groups to receive a CPR course involving one of the three strategies. Then a human simulation took place. 192 schoolchildren (64 per group) were randomly selected and received one of the courses. 182 participants who correctly assessed the victim were compared: 16 (26.2%) out of the 59 participants using RP and checking breathing regularly detected cardiac arrest before the end of the simulation, compared to 41 (67.20%) out of 61 using RP re-evaluating breathing every minute, and 56 (90.3%) out of 62 using head-tilt-chin-lift. Statistically significant differences were found between the RP groups (p < 0.001; OR = 5.766) as well as between the Head-tilt-chin-lift and both RP groups (p < 0.001; OR = 21.094), (p = 0.002; OR = 4.553). The strategy involving head-tilt-chin-lift significantly increased the likelihood of detecting cardiac arrest. Re-evaluating every minute when the RP was used significantly increased the likelihood of detecting cardiac arrest.