2023-24 NFHS Rules require All Wrestlers to wear suitable undergarments which completely covers the buttocks and groin areas under their uniforms that is tightly fitted and not extending below the knee. 

Only the following colors are authorized:

White, Black, Gray, Light Blue, Carolina Blue 

In other words, under garments should not be easily visible due to sharp contrast in colors.

Must be worn at time of weigh-in at the scale!

Females are additionally required to where a sports bra (not regular bras) that completely covers their breasts and minimizes exposure.  

Females may additionally wear compression shirts under a singlet if desired, as depicted below.

Both males and females may wear compression shorts over a singlet if desired, as depicted below. 

Reference:  2023-24 NFHS Wrestling Rules, section 4, "wrestlers classification and weigh-in", page 16