I can't find any comparable stats on just religious schools, but I strongly suspect they are, on average, performing substantially better than non-religious schools. The reasons for that are more to do with the students than the schools, but the exact reason is inconsequential - the point is that people are targeting them because of the religious aspect and not the quality of education.
The typical claim of evolution is illogical. Even if a religious school solely and exclusively taught creationism while not even paying lip service to the controversy (which few to none do), it's not at all like a child's education would be permanently crippled. As the most important things learned in basic education are not facts, but skills - reading, writing, and arithmetic in particular.