Small Business Size Determination-Tiered Corporation

Statement of facts:

Assume a NAICS code size standard of 1,000 employees.

Current sum of all entities is less than 1,000.

Holding company provides corporate services only and allocates costs to subsidiaries.

Four subsidiaries, each an incorporated entity for legal and accounting purposes.

#1 Provides commercial products and services. May 'sell' product or services to subsidiaries via subcontract.

#'s 2-4 are under DCAA cognizance.

Question: Would one roll-up the number of employees to the holding company (as I expect), or could each entity be said to stand alone?

Thank you for your feedback.