Casey Anthony BACK TO SCHOOL

8/26/2011 5:30 AM PDT BY TMZ STAFF
Casey Anthony ain't wasting her time while she serves her probation in Florida -- TMZ has learned, she's going back to college ... on the Internet.

Sources close to Casey tell TMZ, she hasn't decided what field to pursue just yet -- but she's adamant about bettering herself while confined to the Sunshine State ... and wants to start taking online courses ASAP.

We're told Casey will hit the books from the comfort of her own home -- which is doubly convenient ... because after numerous death threats, she doesn't plan to spend much time outside.

And to make sure she stays safe -- we're told Casey has the entire place on lockdown ...with a 24-hour security team.