In TX, I can CC up to the front door of a PUBLIC grade school, but not inside.
In Colorado, the answer seems to be that you cannot CC outside your vehicle at all when on school grounds.
https://handgunlaw.us/states/colorado.pdf
(3) A permit issued pursuant to this part 2 does not authorize a person to carry a concealed handgun onto the
real property, or into any improvements erected thereon, of a public elementary, middle, junior high, or high
school; except that:
(a) A permittee may have a handgun on the real property of the public school so long as the handgun
remains in his or her vehicle and, if the permittee is not in the vehicle, the handgun is in a
compartment within the vehicle and the vehicle is locked