To find out how many students do not participate in any after-school activities, we use the percentage given in the table.
From the table, we see that 10% of the students reported that they do not participate in any after-school activities.
Now, we can calculate how many students this percentage represents:
\[ \text{Number of students not participating} = \text{Total students} \times \text{Percentage not participating} \]
Converting 10% to a decimal:
\[ 10% = 0.10 \]
Now, we calculate:
\[ \text{Number of students not participating} = 210 \times 0.10 = 21 \]
Therefore, 21 students do not participate in any after-school activities.