smc

To begin, we see that the remaining $30\%$ of the students got $95$ points. Assume that there are $20$ students; we see that $2$ students got $70$ points, $5$ students got $80$ points, $4$ students got $85$ points, $3$ students got $90$ points, and $6$ students got $95$ points. The median is $85$, since the $10^{\text{th}}$ and $11^{\text{th}}$ terms are both $85$. The mean is $\frac{70(2)+80(5)+85(4)+90(3)+95(6)}{20}=\frac{1720}{20}=86$. The difference between the mean and median, therefore, is $\boxed{1}$.