The Trainers' School in Sinnoh is located in Jubilife City, east of the Global Trade Station and west of the Pokémon Center in Pokémon HeartGold and SoulSilver. On the right side of the school, there are two School Kids on a blue carpet. They both have a Lv.6 Abra that only knows Hidden Power. After both are defeated, the boy will give away TM10 (Hidden Power).
The other kids in the School have some basic information about the game of Pokémon. Status ailments and their effects are listed on the chalkboard.