[单项选择]

The number of city schools put on a list for strict scrutiny by the state for poor academic performance went up slightly this year. and the number of city schools taken off the list by showing improvement dropped, the state’s commissioner of education announced yesterday.
Ten city schools—now at risk of being shut down—were added to the list of Schools Under Registration Review, known as SURR, bringing the total in the city m 40. Statewide. 61 schools are under review, said the commissioner, Richard Mills. The addition of 10 city schools reverses what had been a trend in the past few years: the number of schools on the list had been falling. There were 55 schools in 2003, 46 in 2004 and 35 last year, an all-time low.
But this year a new factor was at work: The state raised the level of performance required to pass its standards. In addition, 6 of the 10 newly named schools are middle schools--and those schools have for years confounded educators
A. more middle schools are put on the list
B. the standard of review is higher
C. schools resist to improve themselves
D. schools confounded educators for years