SOLVED. Fantasy Children's Series featuring a kid whose chosen as a companion to the spoiled prince[s]

[Linnea]

I have been searching for these books for quite some time. The story follows a young boy who is chosen to be the companion of the spoiled prince. The story starts with the soldiers (maybe) coming to town and making all the young boys take an intelligence test to find a suitable companion for the prince. This boy answers the questions stupidly in order to avoid being chosen. He wants to stay with his mother because it's just been the two of them since his father was punished by the tyrannical king. The prince thinks the boy's answers are funny so the boy is forced to move to the castle and away from his mother.
I'm pretty sure that the current king is not the rightful king and there is a resistance movement, of which the boys father was a part. The way that people are punished is that they are thrown into the moat which is inhabited by dragons. The dragons then drag them underwater and they are assumed dead. The boy makes friends with a girl at the castle and begins to become a part of the resistance. When he is caught, he is thrown to the dragons and discovers that they aren't actually eating the people, but are saving them by taking them into an underwater cavern. Here he's reunited with other people who have been punished and who are serving the resistance.
I don't know the names of the books or the author, but I remember them having brightly colored covers (like light blue and light green, typical easter colors, I guess). I think there were three books, but there may have been four. I'm also pretty sure that I read them circa 1988 because 4th grade was when my reading frenzy really set in. I was listening to the "Private Dancer" album by Tina Turner, which was released in 1984, and to this day when I hear any of those songs I think of these stories.
They are definitely kids books, probably what we call chapter books for ages 8-12, and were probably published in the mid-1980s because they weren't crisp new when I read them.
I would love to find them again. All help is appreciated.

[Debbie]

Is this the Sid Fleishman book where the boy has a specific title for his relationship to the prince. i will look up sid fleishman and get back to you. wait I remember, it was The Whipping BOy. Princes could pick some poor schlub to take their physical punishment for them. Of course since this taught the prince absolutely nothing, whipping boy had to come up with a strategy to do so,

[Linnea]

It's a good guess, but this isn't the story I'm remembering. In the books I'm looking for, the boy doesn't get punished for the prince's misbehavior he just has to be his "friend".

[Tahleen]

Could it have been something by E. Nesbit? I haven't read anything by her but I know she wrote a lot about dragons, though it was probably before the 1980s.

[Linnea]

I'll check out E.Nesbit. Thanks for the suggestion.

[Ros]

Could it be Brill of Exitorn, by Peggy Downing? Fantastic book.

[Linnea]

I think that's it! Yeah! Thank you so much! Now, to find a copy and read it again.