Your child Sim can unlock ‘real’ skills if they max out their child skills: Creativity skill, Motor skill, Social skill and Mental skill.
Children use a different set of Skills than adults do. Children only have four possible skills, and once they transition to Teenagers, their skills are lost.
However, that's not to say that Child Skills are useless. Their skills simply apply bonuses the speed at which they learn other skills as teenagers and adults. Like adults, their skills become Level 1 once activated for the first time, and can be increased to Level 10. Many Child Aspirations are achieved by working on the relative child skills.
Below is an alphabetical list on the four child skills, how they are improved, and what they do.
Child Skill List
Creativity (Child Skill) affects the speed at which they gain all music- and creative-based adult Skills, including Guitar, Painting, Piano, Writing, and Violin. This is increased by working on the activity table.
Mental affects the speed at which they gain all mind-based adult Skills, such as Logic and Rocket Science. This is increased by working on homework, playing chess, and reading.
Motor affects the speed at which children gain body- and dexterity-based adult Skills, such as Fitness and Programming. This is increased by playing on jungle gyms.
Social (Child Skill) affects the speed at which children will gain social-based adult Skills, such as Charisma, Comedy, and Mischief. This is increased simply by socially interacting with anyone, kids or adults alike.