do u have longer shorts?
are u able to wear sweat/track pants?

im not sure of ur uniform requirements

if not able to cover it with clothes
and considering u say ur not good at lying
the thing then to do is u cood use a bandage like others suggest and just say to anyone who asks
i cut myself on something silly
most will not care its high school
and most of what u say is not a lie
(i cut myself)
good luck with it

and never feel ashamed
(((muse)))
ur brave and u can get thru this and be stronger