A student sitting near a bench does not get pulled toward the bench because

Gravitational force is the force exerted by two objects on each other having some mass. It is given by:
$F=\frac{GMm}{r^2}$
Where M and m are the masses of the objects and r is the distance between them.
G is the universal gravitational constant having value, G=$6.67\mathrm{X} {10}^{-11} {\mathrm{Nm}}^2/{\mathrm{kg}}^2$

As we can see, the value of G is very small therefore in order to have greater force, the objects need to be very massive.
Here, if we consider the mass of a boy as approximately 40kg, the mass of the bench as 50kg and the distance between them as 10 metres then the gravitational force between them will be:

$$\begin{gathered} \mathrm{F}=\frac{6.67\mathrm{X}{10}^{-11}\mathrm{X}40\mathrm{X}50}{{10}^2} \\ \mathrm{F}=\frac{6.67\mathrm{X}{10}^{-11}\mathrm{X}2000}{100} \\ \mathrm{F}=13.2 \mathrm{X} {10}^{-10}\mathrm{N} \end{gathered}$$
 

As we can see, the force will be very small. This force will not be sufficient to overcome the friction between the boy and the surface. Therefore, the boy does not get pulled toward the bench.