How Accurate is The ChessKid Rating?

The ratings are less accurate than on Chess.com because the ratings are relative to other players, and ChessKid has a thinner range of skill levels.

I am aware, but how accurate is the rating?

Just like here, the site uses Glicko ratings with a measure of uncertainty, the rating deviation (RD).

So, if a player has a high RD, their rating is likely inaccurate. With a lot of fairly recent games, the rating is probably fairly accurate within the pool of the site's players but may not accurately reflect their rating here or OTB.

Thanks, but on ChessKid you will play a lot of different sometimes people who are experienced and some that are inexperienced (even if you are inexperienced you may get matched up against somebody way more experienced) so sometimes you play people a lot worse or a lot better (that are 1000 higher rated than you, or 1000 below you) and this causes unfair matchups making it hard for a accurate rating (on ChessKid) I have read a few articles and am decently aware of how accurate the rating is on Chess.com. I would to know about ChessKid because the ratings seem very off.

Rating gained from people with large rating differences will be minimal.  The ratings, with a sufficient number of games, will be an accurate reflection of performance within the pool of players. Accuracy is measured within pools and if the past results are aligned with a player's rating, the it is accurate for that pool. 

Accuracy within that pool does not mean that that player's rating there would match their rating on another site or in another pool. Ratings are not absolute values of strength but relative ones reflective of past performance.

The rating is approximately 400-1000 points underrated

That's good!

Is 1000 rating on chess kid good?