By the book there should be either 1 solo tackle credited on a play or 2 assisted tackles. So a team's starting ILB might have 2 solo tackles and 6 assisted tackles for a total of 8 total tackles.
What many high school coaches do, though, is give tackling credit to any kid who showed up to the pile or laid a hand on the ball carrier. So the ILB in our example above might have shown up and made some contact after the ball carrier's momentum was stopped 10 or 15 times during a game, and if his coach gives him credit for those plays he goes from 8 tackles to 23. Tackle stats are hard to trust at any level, but in HS you better be taking them with a heavy grain of salt. When voting for all-district/region/state, coaches should be going on what they saw on tape and during the game more so than the tackling statistics compiled by the player's coach.