In many states, yes, the school is still obligated to implement the IEP, but the parent is usually required to arrange for transporting the child to the school. We recommend checking with your state’s Department of Instruction (specifically, the division for Exceptional Children) and checking for your state’s specific guidelines.
The previous replier had an excellent answer. However, I wanted to add to it, because I am not sure if you (or those who may search this later) are asking if the school has to continue to help provide special needs services or if they have a duty to continue to, even if the parent does not wish them to.
In the former, in most states, the school is required under disability laws, to continue to help meet special education needs (you still pay into the school system, you still have a right to access the help from it).
In the latter- no, the school may not force a parent to accept special education/iep evaluations or help if the parent does not desire it. There have been at least one prior court cases that upheld this (that I am aware of). To which I will include links to of the hslda summary. We chose to use private services and evaluations, rather than public school offered ones, so this is something I am very aware of. I just wanted to mention it- in case anyone else searched this question wanting an answer from this end. It may also depend on your state how much say the school has in your program, so I would check into your individual state laws.
*I am just another homeschool mom, not an expert. HSLDA is a great place to go to ask for legal advice and seek general knowledge, as they are legal experts in the homeschooling field.
**I am including a link that is a good place to start looking for information about individual state laws on disability help and the previously promised link about the court case.
In my state(IA) if you choose to homeschool, you are choosing to no longer have an IEP for your child. The student who had an IEP would be exited from services and would need to evaluated for eligibility if they attended school again. If your state is this way, there is the option to enroll the student into a public virtual school.