My son was evaluated at 18 months, 24 months and 30 months before he began (because, there's not a whole lot they can do for you except give Mommy homework). He began seeing the therapist bi-weekly for about 9 months and then weekly. Just before he turned 3 he was evaluated by our local school district, and it was recommended that he receive about 30 minutes each week. For the remainder of the school year (he turned 3 in March) I took him once a week for 30 minutes. He is now in the PreK program, so he goes to speech twice a week for 15 minutes. I think that's good for him. More often makes it more consistent, and 15 minutes is good for his attention span.
You probably need to check with your insurance and see if this is even covered for a 5 year old. Many, many insurance companies do not cover services once the child is 3 years old. Although ours does, so maybe I'm wrong about that. Either way, find out for sure. Also, if they do cover it, make sure you know which therapists you are authorized to go to.
At 3 years old, the school district has an obligation to your child. You could simply call your local school district and ask them for an evaluation. They are required by law to evaluate him if you ask for it! (My SIL is a Speech Pathologist, and she said that this is required by law. Any parent who wishes to have their child evaluated needs only request it, and the school must provide this service.)
An evaluation is just a series of activities, usually pictures. Your son would be asked questions about the pictures. This is to see which sounds he is making correctly, which he needs to work on, whether or not comprehension is an issue, etc. The therapist will make notes and score everything. At a later date the therapist will sit down with you and explain the findings - what he did well, what he was not able to do, what is recommended based on that. It could be once a month, it could be twice a week, it could be wait and see and evaluate again in 3 months. Just depends on what they notice and what is "age appropriate."
It really isn't a big deal at all!!! The only thing that was a challenge for me was finding a time that fit around my work schedule. But let's face it, that's life as a parent!
I would really consider calling the school. This year has been so wonderful for me with my son's speech therapy just being a part of his school week. And I know that even if next year he has a different therapist (and some schools only have one), at least he will be familiar with the room and the procedure and just be so much more relaxed. This is his school and will be for 8 years, so it's great to get him started there. I was so happy that I was able to come to his school for an hour last week and was able to meet with his speech therapist. So great to meet her and see how he's doing and how they are together! Made me feel so much better about everything.
My son is 3 1/2 now. He is doing amazing! He still has work to do, but it's coming along. He's happy in school, and his speech is just so much clearer.
Try not to worry. This is really important. The sooner he corrects these errors, the better. This can effect his comprehension, his ability to effectively communicate. As he learns letters and phoenix, this will effect his ability to learn to read and to learn how to spell. My oldest had to work on the "th" sound, and he tells me how he used to thing the number 3 was spelled "free." Makes sense since he didn't realize that there was a "th" sound.
This is a good thing! Try not to worry.