making kids compete with adults for jobs that the latter should only be doing.

Of course, they didn't have sociology and stuff like that back then to study this, so we don't know for sure.

I believe that a short term impact of child labor was that the industries that used child labor were able to grow quickly.  Part of this was due to the low price of child labor.   Another short term impact was, of course, on the children.  They were forced to work in hard and dangerous conditions, which must have been quite unpleasant.

In the long term, I think that child labor's impact was not so bad.  As the industries became more profitable, people's standards of living grew.  The companies innovated and were able to start doing without child labor as they got richer.  I think that is one reason why children in the rich world today work less than those at any previous time and place in history.

I agree with the first answer.  But I would add one thing.

The first answer says we have to remember that those days were not like today and so we must not hold them to our values.  But we also have to compare those days to what came before.

It is true that kids had always been expected to work.  But before the Industrial Revolution, that work had always happened at home, within the context of the family's work (farming, mostly, but other things too).

Once industrialization came, the kids were expected to work, but now they were working away from their family and under the supervision of strangers.

This put stress on the families because it was a very different social situation than had existed before.

It's important to remember that we look at child labor as immoral and unethical for companies to practice or parents to allow, so much so that we outlawed it early in the 20th century. At that time, during the Industrial Revolution and into the early 1900s, people viewed it as a fact of life, as one of the few ways a family, especially an immigrant family, could earn enough to survive.  Education had much less value than working did. 

So the way it affected society was that it denied children education, was dangerous to them physically, and put further stress and strain on the family unit as individual members were isolated and separated day to day.  There were labor activists fairly early on in the industrial revolution, but they were shouted down, beaten down or made illegal into the late 19th century, and achieved almost no success at all.

I am going to assume this question is asking about the prevalence of child labor during the Industrial Revolution in England, the reasons for this and the reaction to it. In the early days of the Industrial Revolution, huge numbers of factories were built, which drew many families from country villages into the cities, where there was great demand for workers, and conditions were crowded and unhealthy. In order to afford to live near their new places of work, many adults put their children to work in factories and as chimney sweepers. While apprenticeships had always been common, never before had children as young as four been working fourteen hour days doing repetitive, low-skill tasks for a low wage. Children worked in coal mines and cotton mills, were put up chimneys, and died from the poisonous effects of the matches they sold.

Labor laws were introduced initially to constrain workers in cotton mills, but it was only stated that those between 9 and 16 could not work more than twelve hours a day. At first, these laws were not even followed. A series of labor laws were successively passed over the course of the 19th century as public reaction to child labor grew increasingly negative, but children continued to work throughout the period of heaviest industrial growth, which had a negative effect on literacy and health. Only the enforcement of the Education Act really saw child labor begin to taper off. The works of writers such as Blake and Dickens tackle this social issue.

During the British Industrial Revolution, children went to work in factories and mines, where their small hands and lower wage requirements were prized. The average age at which children went to work was 10. In factories, children worked as piecers, repairing broken thread that went into machines, and as scavengers whose job it was to clean factory machines. In mines, children minded trap doors and carried axes for older workers. In cities, children worked as chimney sweeps and errand boys.

The work was dangerous and dirty, and it provoked a public and literary outcry. For example, several of Charles Dickens's characters, such as Oliver Twist, show the degraded lives of children in the Industrial Revolution. Reformers such as the Lord Ashley, the Seventh Earl of Shaftesbury, led the crusade for child labor reform in the British Parliament. Two main reform bills were passed--the Factory Act of 1833 and the Mines Act of 1842. The Factory Act set the minimum age of labor at 9 and limited the hours children could work, and Mines Act set the minimum age of mine workers at 10. These acts basically started to end the use of child labor, and that has affected our current-day practice of largely eliminating child labor and regulating labor for the few children who work for wages. 

When children had to go to work in factories during the Industrial Revolution in Britain, there were many effects.  The children themselves were effected.  Their families were also impacted by it.

Usually when children went to work in factories, they did so because their family needed the extra income.  Their work had a positive impact on their families in that they were able to provide money for the household.  Factory workers were usually poor, and because of this any extra income was beneficial.

Children were impacted in negative ways by factory work.  Children who worked in a factory day after day were unable to attend school.  Working in the factory was often dangerous.  Small children were frequently sent into small spaces under and around factory machines to pick up things that had fallen, such as pieces of cotton.  Machines could be dangerous because there were few safety features.  Young girls had to wear their long hair pinned up because it could get caught in the machines.  This could injure or kill them.  The pollution caused by the factories could make children ill.  Many children became ill or died from what was called "mill fever."