does 3 grader qualify for stident discount on macbook air

Education Pricing and Student Discounts - Education - Apple

It looks like the education pricing is only for

• Current and newly-accepted college students
• The parents of current and newly-accepted college students
• Home school teachers of all grade levels

So, no, there's no special discount for 3rd-graders.

As for trade-ins, see Apple Trade In - Apple .

See the following from Education Pricing and Student Discounts - Education - Apple

Save on a new Mac or iPad with Apple education pricing.

Available to current and newly accepted college students and their parents, as well as faculty, staff, and homeschool teachers of all grade levels.

For trade-in information, see: Apple Trade In - Apple

Education Pricing and Student Discounts - Education - Apple

Trade-in estimator: Apple Trade In - Apple