Here are the sentences with the identified mistakes and their corrections:

1. When babies are around fifteen months old, they can pick up objects and put themselves into small boxes.
**Mistake:** themselves
**Correction:** themselves → themselves into small boxes. (Correction needed: "themselves" is not incorrect in context, no change required.)

2. The wooden fence surrounded the factory was beginning to fall down because of the heavy storm.
**Mistake:** surrounded
**Correction:** surrounded → surrounding

3. It is common believed in the United States that school is where people go to get an education.
**Mistake:** common
**Correction:** common → commonly

4. The mass media has a strong social and cultural impact upon society.
**Mistake:** has
**Correction:** has → have

5. Most every job today increasingly requires knowledge and experience.
**Mistake:** Most every
**Correction:** Most every → Every

Feel free to ask if you need further assistance!