Whether Jewish children are permitted to listen to or use electronic media depends on the particular version of the Jewish faith their parents follow. While all Jews take the Torah (the Old Testament of the Bible) as their sacred text, different types of Jews interpret it differently. There are three major kinds of Judaism common in the United States:
Reform: This is the most liberal movement in Judaism and most common form of Judaism in the United States, and accepts the scholarly consensus that the Torah was written over a period of many centuries by human beings (perhaps under divine inspiration), and that Jews need to adapt themselves to the modern world. In general, they do not adhere to many of the traditional ritual laws concerning restrictions on food, limitations of activities by gender roles, or restrictions on activities on the Sabbath (Saturday). Reform Jewish children are not forbidden to use media, although their parents, as any other responsible parents, may restrict use of media on school nights or until after the children have finished their homework.
Conservative: Conservative Jews occupy the middle ground between Reform and Orthodox, believing that Jews should observe the ritual laws called halakhah, but they should be adapted to modern society. While they might not forbid all use of media, they might forbid using media on Saturdays or during certain of the Jewish holidays, and restrict their children from engaging in online activities or watching videos that involved nudity, obscenity, strong language, or violence. Of course, many non-Jewish parents feel the same way -- Christian, Hindu, and atheist parents alike might not want a sixth-grader watching pornography.
Orthodox: Orthodox Jews are the only group within the Jewish community likely to forbid their children all access to media. Their reasoning is based on several things. First, they believe strongly in modesty, and don't want their children seeing the explicit sexual content that one finds in much contemporary music, television, and videos, or have their children seeing explicit content shared via smartphones, or participate in sexting. Second, many orthodox Jews believe in siyag latorah (building a fence around the Torah), or keeping their children away from all the temptations of modern life to preserve their faith.