After a century of educating women, Sweet Briar College in rural Virginia announced this month it would close. Its endowment of about $84 million did not protect the school from the financial strains of declining enrollment. Some higher education experts warn Sweet Briar is part of a national trend of declining student interest in expensive liberal arts education and single-sex schools in place of more vocational degrees. The challenges many small private colleges face, what some schools are doing to attract students, and if it matters.