You do not ever know; you just have to trust your gut.
What will happen next year? If a fifth grade student needs a placement with almost a 1:1 ratio of adults to students, he is very unlikely o be able to manage included in a typical middle school which is a brutal experience for many, including some PCs.
IF you like this placement, the relevant question is, "Can he go there next year, too?" If the answer is, "No," then what is the plan for next year? I would suggest you look at the equivalent program for middle schoolers to see if you are favorably impressed with it, also. If no such program exists, then I think you have a larger problem than whether to go or stay this year.
Martie