\begin{Schunk}
\begin{Sinput}
 t.test(gradrate ~ schtype, data = dat)
\end{Sinput}
\begin{Soutput}
	Welch Two Sample t-test

data:  gradrate by schtype
t = -15.9578, df = 994.788, p-value < 2.2e-16
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
 -17.87557 -13.96064
sample estimates:
 mean in group public mean in group private 
             50.18203              66.10013 
\end{Soutput}
\end{Schunk}
