I would say that an A8-4500 running at 2.8GHz would be about equal to an Intel mobile CPU running at 2.2GHz - 2.3GHz, but that's a rough estimate. Individual tasks can vary though. The A8-4500 is a quad core CPU while most mobile Intel CPUs that would compete with the A8-4500 on price would be dual core CPUs.
If you were to use the laptop for video encoding which can take advantage of 4 cores (depending on the program and video codec), then I would say it would be just a little slower than a Core i5-2410m running at 2.7GHz. Otherwise, the A8-4500m would be about equal to the 2.2GHz Core i3-2330m CPU.
A 7th grader would mean a child of about 11 years old (+/- 1 year) so I recommend a light laptop if he/she will be carrying it around with him/her. Therefore, I would go with the HP Envy Sleekbook 6z which weighs in at about 4.75lbs compared to about 5.5lbs for the HP Pavilion dv6-7010us. But 4.75lbs is still a bit heavy for a 7th grader to carry around in my opinion.
The HP Envy Sleekbook 6z comes with a dual core A6-4455m which should be more than enough for a 7th grader to do homework, surf the net, and watch movies. It's modest integrated Radeon HD 7500g graphic core is good enough to play some games with a mix of low/medium quality settings on a 1366x768 resolution screen.