Washington, D.C., Mayor Adrian M. Fenty's plan to take direct control of the city's public schools would give the City Council one measure of authority other big-city mayors held onto when they took over their school systems: line-by-line control over the budget. Whether such power is a plus is a matter of debate among educators, legislators in other cities and those on the D.C. Council, where at least three members aren't sure they want it.