Well from what I see there your bandwidth is low. It could be any number of the following:
1.) More than 1 computer using your internet
If you have multiple computers on the same modem then you could experience lag if they are streaming movies or downloading/uploading.
2.) Interference in your wireless signal
A number of things can interfere with a wireless signal, from microwave ovens to wiring in your walls. Try directly plugging your laptop into the modem via ethernet cable.
3.) Bad phone lines
If you're the only PC/laptop on your network AND you still experience lag when you hard-wire into the modem then you could have a bad telephone wire/jack. Try replacing the telephone line with a 8ft or shorter line.
4.) Applications on your computer downloading/uploading files
Be sure you turn off torrent programs and other programs that could be updating/downloading in the background.
5.) Fixable problem on your ISP end
You might want to get in touch with AT&T Tech Support(they're available 24/7) and ask them if it's a problem on their end
6.) Your ISP has over-sold internet in your area
If all else fails, it could be that AT&T has just over-sold internet in your area and you're having a latency outage during peak hours. They won't openly admit this without harassment, but if this is the case ask about their 60% rule and get a discount on your bills until the problem is fixed.
