Short answer. Only in narrow, permitted situations and only on conditions the Labor Code no longer states. Republic Act No. 9231 (2003), amending Republic Act No. 7610, governs child labour now: it restricts what the child may do, requires a work permit, caps hours and requires schooling to continue.
What the law says
except when he works directly under the sole responsibility of his parents or guardian, and his employment does not in any way interfere with his schooling
Labor Code, Article 139 — Minimum Employable Age. Read the full provision →
The sentence people rely on
Article 139 of the Labor Code bars the employment of a child below fifteen except when he works directly under the sole responsibility of his parents or guardian, and his employment does not in any way interfere with his schooling. That is the sentence families point to when a child helps in the store, the stall or the farm. It is no longer the rule. Republic Act No. 9231 (2003), which amended Republic Act No. 7610, now governs child labour and is materially stricter than the article above. The Code text is reproduced on this site as history, not as a permission you can rely on.
What the current Act adds
Under Republic Act No. 9231 the exception is not a general licence for family work. The permitted undertakings are restricted rather than left open, a work permit must be obtained from the labour department, working hours are capped, and the child's schooling must continue rather than merely not be interrupted. Those are conditions with teeth, and all of them have to be satisfied together. The exact limits, the permit process and the documentation required are set out in that Act and the rules issued under it, so read them there before treating any arrangement as lawful.
Supervision by a parent is not the whole test
The most common misreading is that a parent's presence cures everything. It does not. Two limits survive regardless of who is supervising. The work must not be hazardous or deleterious, and the education of the child must genuinely go on. A child kept out of school for the harvest, or put on machinery because a parent is standing nearby, is outside the exception whatever the family understanding is. The protection exists for the child, so it is not something a parent can waive on the child's behalf.
If you are the parent, or you have seen it happening
If you run a family enterprise and a child under fifteen helps in it, the honest step is to check the arrangement against Republic Act No. 9231 and its rules: whether the undertaking is a permitted one, whether a permit is required and has been secured, what the hour limits are, and how schooling is protected. If you are worried about a child working elsewhere, child labour is enforced through the labour and child protection framework rather than through the repealed Code text. This page is general legal information and not advice on a particular household or business.