Often, as parents, we find that we are the last to know if there is a problem, especially at school. We don't discover there are issues until the mid-term or report card come home or after they have all ready failed the test. Then, there is anger and frustration, a panic to find solutions - many things run through the parent's brain. Your student is also upset and the worst thing ever - you may all ready employ a tutor.
This is a worst case scenario of course, but many parents hire a tutor to simply get their kid through the homework and then the student fails the test. Did you just waste a lot of money? Maybe... Or did you overlook the fundamental function of the tutor? Most likely.
I would love to say that tutors can be anybody. And anybody can get your kids through a homework assignment as long as they know how to do it already. That's easy. The hard part is figuring out where the gap in knowledge is and filling it in so it doesn't exist. This is one of the main factors, especially in math, where a tutor may fall short.
Most evaluative testing can be pricey, but the sign of an effective tutor is that they have some way to diagnose these knowledge gaps. After seeing the gap, they also go beyond homework help. They may help them understand how to do the assignment and leave the last fifteen minutes of a session dedicated to filling in those gaps if they are small. For example, if your student is in Algebra and doesn't know their times tables, it doesn't matter how much homework help they get, they will always be two steps behind until they learn their times tables. There are no shortcuts in many subjects. Good tutors know this and fix the gap - money much better spent because then the tutor has helped them long term and not just during their homework session.