There are two parts to this answer:
1. If the middle school participates in interscholastic extracurricular activities governed by a statewide organization, such as The Florida School Music Association (FSMA), then the school must allow the student to participate in the band class.
2. If the middle school is not a member of the FSMA, then the student could participate if the school district has a part-time enrollment policy which permits home education students to take classes on a part-time basis at a public school. Some school districts have part-time enrollment policies and others do not. Generally, the home education contact at the school district would know if the school district has a part-time enrollment policy.