paragraph: Philips Andover Academy, one of the most elite and selective boarding high schools in the country, failed again to elect a girl to its top student position -- the school presidency. Since the school went co-ed in 1973, only three girls have held this office. In a letter that launched a fiery debate across its campus, senior girls implored their peers to look hard at the school's "staggering gender imbalance" in student leadership. Headmaster John Palfrey responded by telling The New York Times, "Girls have not had equal access to top leadership positions." Yet, access for girls is rarely the problem when it comes to pursuing leadership. Feeling authorized to take leadership roles is the problem. It starts early. From childhood to adolescence, girls face mixed messages about displaying power and authority. The girls at Andover and elsewhere are socialized to be likeable, to please others, to not tout their own successes and to speak softly like proper girls. As a result, they face powerful psychological barriers to attaining leadership roles. The impact of what I call the "curse of the good girl" effect first appears in friendships, when young girls take pains to avoid direct conflict with peers. "I want to tell her how I feel," a typical girl would say in my research interviews, "but what if she hates me or turns other people against me?" These girls often resorted to gossip and other forms of indirect communication, or they internalize their feelings in unhealthy ways. Over time, pretending not to be angry with a friend when you are, or turning to a text messages instead of having an honest conversation, becomes a formative habit of communication. Meanwhile, the muscles that girls need to assert their strongest feelings and opinions atrophy. By the time girls join sports teams and school organizations, many have imported these social habits into student leadership contexts. 
question: What has caused the psychological barriers to attaining leadership roles for girls at the Academy?
answer: Men control who gets to be in leadership roles at Andover