She attended and swam for Ursuline High School in Santa Rosa her freshman and sophomore years. She swam for the Santa Rosa Neptunes Swim Club in Santa Rosa from age 12-15.[1][2] She is an alumna of Whittier Christian High School, where in 1984 she set the national record of 53.95 seconds in the 100-yard butterfly and the D1 record of 23.07 seconds in the 50-yard freestyle. While living in Southern California, she trained at the Industry Hills Aquatic Club in the City of Industry, California.[3] She received an athletic scholarship to attend Stanford University, where she swam for the Stanford Cardinal swimming and diving team in National Collegiate Athletic Association (NCAA) and Pacific-10 Conference competition. As a 19-year-old, she received the Honda Sports Award for Swimming and Diving, recognizing her as the outstanding college female swimmer of the year in 1985–86, was a runner-up for the award the following year and won again in 1988–89.[4][5][6]
Johnson made Rivals.com's list for the "Top 100 Female Athletes In State History."[7]