most of the big tutoring centers do not work well for people who are actually struggling with maths - the pace is way too fast, their actual problems can't really be worked on (most common one i see is algebra), and since most centers work at least a term ahead, once they decide they need help, its usually too late to join since they'd have to catch up a term.
i honestly cannot see the utility of going to a large tutoring center for math when there is little leniency for incomplete homework, when students do poorly in tests they are asked to leave the center, where external support is often required to complete the work, and in some cases completely out of syllabus stuff is taught (cough du). small group/individual private tutoring allows you to actually work on the things you need help with.
for students who already have the ability, just need motivation and discipline, or don't know how to use the free resources available to them (past papers), tutoring centers work very well. except, there are many other strategies that can be used, that cost a lot less...
i say this as someone who goes very very well in maths without tutoring and has seen over a dozen people struggling in maths going to one of the large tutoring centers for math and subsequently leave due to not getting the help that they need and in some cases in a worse mathematical state than when they went in. a majority of people i know who went to small group private tutoring saw an improvement in their marks and a solidification of previously unstable mathematical foundations.
If you are struggling and are having trouble with concepts, you need specialised help, from a tutor or teacher. If you are stagnant in your exams, you probably need to improve your study habits/routine. If you are already achieving solid marks, by utilising the freely available resources, and a textbook or two, and exercising a bit of self-discipline, you can do very very well. It is my strong opinion that tutoring centers are only a good use of money for a very small band of people.