I was asked what has the greatest impact on children's future academic abilities. If we are talking about overall academic abilities I would highlight the following:
1. Sing with and to children. It helps with sentence structure, word tone and grammar, it helps with social competence and developing self esteem. I could go on but this gives you as good start.
2. Read with and to children. Also read both at the child's level as well as at levels above the child's level. This applies for ages 1 - 12. Reading builds comprehension. If you can read you can do anything. If you can't read you can't do math, science, social studies, etc.
3. Play with children - play is what helps children make sense of their world and process complex information.
4. Ask children questions. Young children ask a lot of questions and parents answer some and get frustrated at times. Turn them around and ask children questions. If a child says, "Why does the wind blow?" you should ask them why they think it blows. Find out what they think. Look for places where you can fill in the gaps in their knowledge. Don't overfill. Sometimes adults try to give too much information. Give information and let them ask the next question.
5. Help them develop a sense of wonder about their world and look at things in new ways. How might a bunny see the world? What would trees see? What is inside an ant hill? This will open their minds to their own questions.
6. Use real words for things and provide labels. Encourage scientific examination and observation.
7. Parents have the opportunity to be their children's first teachers. What you give or don't give is not related to income, or social status. Anyone can visit a museum, a park, or a store to help explore a child's world.