On one hand, you do not get any more points for a jumping kick than you do for any other kind of kick. However, there are times when a jump is better than a standard kick, you just have to be good at not telegraphing your intentions.
The side kick is a good example. Assuming you decided to throw the side kick instead of any other, then you want to kick with the lead foot - it's closer, quicker, and harder to see coming. You could shift your weight back and throw a standing front leg kick, but that will rob you of distance. The only other alternative is to jump. (Technically, you want to hop or gallop; a jump implies throwing your rear knee forward. That's not what you want, that's too slow and easily countered.)
Now, you did say "jumping side kick", but you didn't mention whether or not a turn was involved. Turns make the kicks more risky (because physically, they strain the ankle and knee; and technically, you're vulnerable to a counter). But the rewards are much higher: you get one or two more points for a turning kick than you do for a non-turning variant. See the rules on points here:
- One (1) point for a valid punch to the trunk protector
- Two (2) points for a valid kick to the trunk protector
- Four (4) points for a valid turning kick to the trunk protector
- Three (3) points for a valid kick to the head
- Five (5) points for a valid turning kick to the head
- One (1) point awarded for every one “Gam-jeom” given to the opponent contestant
You can find these points listing here in the current World Taekwondo rules, these are published April this year. Jump to page 25, under "Article 12", section "3".
World Taekwondo Rules - April 2018