"impact aid" means: Money provided by the government to school districts that have lost property tax revenue due to the presence of tax-exempt Federal property.... This is technical or formal vocabulary, more likely to appear in school work, news or a particular profession than in peer chat. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. If your child uses the term, it is usually a sign of curiosity about a subject area. A short follow-up question about where they came across it is usually all that is needed.