Thanks for all the suggestions!
I have been to Community School of West Seattle last month for a class tour and liked it there, so I submitted the application form including a non-refundable $50 registration fee. I asked for a sliding fee since they offered that on their form.
Then I received a letter from them last week that they have rejected my application. The reason given was that they are trying to make more room for three-year-old kids and since my son is almost four, they couldn’t accept him. They did not say they would put me on a waiting list if there’s any cancellation.
I personally think it’s probably due to the fact that they didn’t want to offer me the sliding fee hence we’ve been rejected. It really disappointed me.