It is a good move to make child labour illegal. But what else would such children do to sustain themselves and their families? There is no point going to government-run free schools when one does not have even food to eat.
The schools provide lunch but what about other meals and what about the family starving behind? Abolishing working of children under 14 years of age would only increase their problems.
First of all such a measure is difficult to implement and even if it is such children would resort to begging or theft which is in no way good for them or the society.