Short answer. The support legacy is paid first. When an estate cannot cover all legacies, the law sets a fixed order of priority, and legacies for support rank ahead of legacies for education — so the support legacy must be satisfied before anything is left for the education legacy.
What the law says
If the estate should not be sufficient to cover all the legacies or devises, their payment shall be made in the following order: (1) Remuneratory legacies or devises; (2) Legacies or devises declared by the testator to be preferential; (3) Legacies for support; (4) Legacies for education; (5) Legacies or devises of a specific, determinate thing which forms a part of the estate; (6) All others pro rata.
Civil Code, Article 950 — Order of Payment When the Estate Falls Short. Read the full provision →
The law sets a fixed order when the estate falls short
When the estate is not enough to pay every legacy or devise in full, the law does not leave the outcome to guesswork or to whichever legatee asks first. It fixes a ranked order in which the available estate must be applied: remuneratory legacies come first, then legacies the testator expressly declared preferential, then legacies for support, then legacies for education, then legacies of a specific determinate thing, and finally everything else, paid pro rata if anything remains.
Support outranks education directly
Within that order, a legacy for support occupies the third rank, ahead of a legacy for education, which sits fourth. So where the estate can fund one but not both in full, the support legacy is entitled to payment first. Only what remains after the support legacy is fully satisfied is available for the education legacy — the estate does not split proportionately between the two ranks the way it does among legacies that share the same rank.
What comes before, and what this does not decide
Both support and education legacies still yield to remuneratory legacies and to any legacy the testator specifically declared preferential — those two categories are paid ahead of both. This rule also does not decide how much of the estate is available in the first place, since that depends on separate rules about debts, compulsory heirs' legitimes, and other prior charges against the estate; it only fixes the pecking order once it is clear the remaining estate cannot cover every legacy in full.
Why the ranking is arranged this way
The order reflects a rough hierarchy of need and obligation: legacies rewarding services already rendered come first, then whatever the testator singled out as a priority, then the practical necessities of daily living, then the longer-term investment of an education, and only after those does an ordinary specific bequest or a general legacy get its turn. Placing support ahead of education fits that logic — a legatee's immediate means of living is treated as more pressing than funding a course of study, even though both are recognized as legitimate objects of a testator's generosity.