While many students in the Forsyth County school system probably aren’t ready to head back to class on Aug. 9, retailers are prepared to sell them all those necessary school supplies.According to a survey conducted by the National Retail Federation, spending for kindergarten through 12th grade and college nationwide is expected to reach a record of nearly $84 billion this year. It also noted that the average family with school-age children likely will spend nearly $700 on supplies. That doesn’t surprise Steve Reid, manager of Super Target on Market Place Boulevard in Cumming.“Back to school is the largest [shopping period] between the summer holidays and Thanksgiving,” he said.