Read the story - the supply distribution was limited to students who attend Likelike during the regular school year. These are students who live in one of the poorest school districts in the State. Students who are not full-time Likelike students (I assume that they are from outside the district or can afford private schooling) were excluded. The school did not exclude specials needs kids specifically.

The school was probably on lockdown since autograph seekers were expected to be roaming the campus and the school wanted to make sure the other kids were kept safe with a bunch of visitors on campus.

You make it sound like the school didn't want kids with disabilities meeting Marcus. How would the kid feel if he got to meet Marcus but wasn't given any school supplies because he's not poor?