Which one is correct?
"have a great impact at students" or "have a great impact for students"?

Some examples from the web:

• Our top athletes' eating habits have a great impact on health and performance.
• It is a crucial component, because an ageing population will have a great impact on future budgetary positions.
• There is certainly a need to act in numerous areas that have a great impact on the whole of European industry.
• Well, the euro will have a great impact on them and it is they who deserve our special attention.
• The outcome of the elections will have a great impact on the EU's relations with Ukraine, either in the positive or negative sense.
• This is reasonable because weather conditions, for example, can have a great impact on annual emissions, linked among other things to the small quantities of hydroelectric power generated in dry years.
• Whilst the single currency will have a great impact on the lives of our citizens, employment is even more immediately crucial for every family in the European Union.
• Especially with this latest Council, there has been a step forwards that we regard as decisive and which may have a great impact on our emergence from the crisis. I would therefore also like to pass on our congratulations for having achieved an agreement in that area.
• emphasises the importance of S&T cooperation with neighbouring countries, which can also have a great impact on regional development within the EU area.
• If we in this Parliament support the inclusion of an article referring to sport in the new Treaties of the European Union, we may have sport programmes which have a great impact, and this would benefit all of us.
• This is indeed a strategy that will have a great impact on Europe in terms of both growth and employment, and one that should ensure great progress in terms of the continent's economy.
• Classification of incinerators as efficient or inefficient in energy terms will have a great impact on these installations and the legislation that directly affects them, in the same way as other legislation such as the directive on landfill.
• They can reveal important facts not just about the person examined, but also about the members of his or her family and, in the final analysis, have a great impact on individual lives and lifestyles, not least as regards decisions to have children.
• Processing firms are very small and are situated in rural areas where they have a great impact on the local economy and on the development of those areas.
• A significant sum could be raised by applying significant leverage through the EIB, the KfW, the Deposit and Loan Banks and other financial institutions, and this could have a great impact on the start-up of projects considered valid and given economic and environmental priority.
• While there has been a small increase in the number of vessels, there has actually been no increase in the total capacity allowed, so I do not believe that this agreement will have a great impact on the number of fish caught.
• - They have a great marriage.
• The Commission is aware that dolphins have a great intelligence and pronounced social behaviour.
• I just want Phyllis to have a great day.
• Tell him/her that we have a great attack.

Some examples from the web:

• Our top athletes' eating habits have a great impact on health and performance.
• It is a crucial component, because an ageing population will have a great impact on future budgetary positions.
• There is certainly a need to act in numerous areas that have a great impact on the whole of European industry.
• Well, the euro will have a great impact on them and it is they who deserve our special attention.
• The outcome of the elections will have a great impact on the EU's relations with Ukraine, either in the positive or negative sense.
• This is reasonable because weather conditions, for example, can have a great impact on annual emissions, linked among other things to the small quantities of hydroelectric power generated in dry years.
• Whilst the single currency will have a great impact on the lives of our citizens, employment is even more immediately crucial for every family in the European Union.
• Especially with this latest Council, there has been a step forwards that we regard as decisive and which may have a great impact on our emergence from the crisis. I would therefore also like to pass on our congratulations for having achieved an agreement in that area.
• emphasises the importance of S&T cooperation with neighbouring countries, which can also have a great impact on regional development within the EU area.
• If we in this Parliament support the inclusion of an article referring to sport in the new Treaties of the European Union, we may have sport programmes which have a great impact, and this would benefit all of us.
• This is indeed a strategy that will have a great impact on Europe in terms of both growth and employment, and one that should ensure great progress in terms of the continent's economy.
• Classification of incinerators as efficient or inefficient in energy terms will have a great impact on these installations and the legislation that directly affects them, in the same way as other legislation such as the directive on landfill.
• They can reveal important facts not just about the person examined, but also about the members of his or her family and, in the final analysis, have a great impact on individual lives and lifestyles, not least as regards decisions to have children.
• Processing firms are very small and are situated in rural areas where they have a great impact on the local economy and on the development of those areas.
• A significant sum could be raised by applying significant leverage through the EIB, the KfW, the Deposit and Loan Banks and other financial institutions, and this could have a great impact on the start-up of projects considered valid and given economic and environmental priority.
• While there has been a small increase in the number of vessels, there has actually been no increase in the total capacity allowed, so I do not believe that this agreement will have a great impact on the number of fish caught.
• - They have a great marriage.
• The Commission is aware that dolphins have a great intelligence and pronounced social behaviour.
• I just want Phyllis to have a great day.
• Tell him/her that we have a great attack.