Como dizer "ficando pra trás" em inglês

I would say "to be left behind" means "ser deixado para trás", to use it in the present continuos would be " (name or pronoun) being left behind".

Falling behind I actually have never heard before.

Olá Tivfroa,

Neste contexto:

She fell behind in her studies.(Ela ficou para trás nos estudos.)

Boa sorte!

Thanks Gabi and Donay!

Gabi, I saw it used this way in this sentence:
You say I'm falling behind E que estou ficando pra trás

http://letras.terra.com.br/the-killers/ ... ducao.html

Yes, it's ok to use "falling behind" as well:

He was falling behind everybody else in class.

Regards