Too much computer and Internet use is bad for your grades, especially if you are young and poor: Results from the 2001 Brazilian SAEB. - Jacques Wainer; Tom Dwyer; Rodrigo Silveira Dutra; Andre Covic; Valdo B. Magalhães; Luiz Renato Ribeiro Ferreira; Valdiney Alves Pimenta; Kleucio Claudio (Comput. Educ., 2008)