In Texas ARD stands for Admission, Review, and Dismissal. This is the meeting where decision are made about special education for a child, and often an IEP (Individual Education Plan) is developed. Texas is the only state to use the term ARD. Other states simply call it an IEP meeting.
Section 504 is a portion of federal law that makes sure kids have access to education, and are not discriminated against in educational settings. This law requires PK-12 schools and post-secondary institutions to provide reasonable accommodations so a student can participate in their education and receive the same benefit as their peers. Disputes under Section 504 are handled by the Office of Civil Rights.
An IEP is an individual education plan. It is developed under the federal IDEA law.(Individuals with Disabilities in Education Act) An IEP has many requirements for evaluations, progress monitoring, specially designed instruction, annual reviews, and much more. Disputes in this process are handled through Due Process. This can include reconvened meetings, mediation, due process hearings, and state education agency complaints.
That depends. If your child only requires accommodations in order to have equal access at school, and does not need ANY special instruction, changes to the curriculum (including additions), a 504 plan may be appropriate. Otherwise, an IEP can provide specially designed instruction, accommodations, AND modifications for children with disabilities.
Accommodations change HOW a student learns. This could include note takers, having tests read, interpreters, extended time, scribes, shortened assignments etc.
Modifications change WHAT a student learns. This could include remedial education, extended curriculum, changed assignments, pull out services, and more.