DS went there for 1-2 months a few summers back for math help. What I noticed was Sylvan "tests" the kids. Although my son scores average/above average during testing at school, Sylvan had him 2-3 grades BELOW and said it would take them 9 months (at roughly $500/month) to get him to the current grade level (which of course would be 9 months behind by the time they finished). He enjoyed going, but didn't seem to make the progress I was hoping for for $500 a month. Sylvan says the kids go at their own pace and that they have to take the kids to the "beginning" and start teaching them from scratch. We felt Sylvan was taking advantage and could tell us whatever they wanted about his progress and could keep us "behind" for as long as we paid them. We asked his teacher for assistance and she gave us the numbers of student teachers she had worked with and had visited the school. Most are anxiously looking for any extra income. DS started seeing a student teacher 1-2x/week for 30 minutes at a time. Since the teacher was well aware of homework (since he student taught at the school) my son only needed 1-2 months of help and he remains above average in math.
I'm sure many have had wonderful and positive experiences at Sylvan. For us, he did better with a private tutor. Our son spent less time "catching up from Sylvans perspective" and more time focusing on his current assignments. We saved money, he got 1:1 attention, and his math grade improved immediately, compared to GETTING WORSE after 2 months at Sylvan (since they didn't focus on his current math, but math he learned 2-3 years earlier). If we would've stayed and done it Sylvan's way, he'd still be behind.