At the national junior championships in 2014, McLaughlin placed a close second behind Shamier Little in the 400-meter hurdles; her time of 55.63 s was a national high school freshman record and a world age-14 best. She would have qualified to represent the United States at the 2014 IAAF World Junior Championships but was a year too young to be eligible. McLaughlin also set a world age group best of 13.34 s in the 100-meter hurdles over 76.2 cm (2 ft 6 in) hurdles that summer.

In 2015, she improved her 400-meter hurdles best to 55.28 s at the national youth trials; the time was an age 15 world best, and she ranked second on the all-time world youth list behind Leslie Maxie’s world youth best (and national high school record) of 55.20 s set in 1984. She qualified for the World Youth Championships in Cali, Colombia, where she won gold in 55.94 s; she finished the year as the world youth and junior leader in the event.