Teaching objects are material evidence of scientific and pedagogical culture and practices. In Portugal, the role of natural history museums and collections created in secondary schools is still considerably unknown, although their importance is recognized. These collections were broadly used to support teaching in biology, botany or geology, however their constitution and development remains largely unstudied. Today, secondary schools hold important collections, almost intact for decades although inaccessible to researchers and the public at large. This paper presents ongoing research on the natural history collections of Portuguese secondary schools, as far as constitution, organization and use through time are concerned. From 1836, when secondary education was established in Portugal, to 1928, secondary schools apparently had autonomy to purchase materials considered important to fulfill governmental and curricular directives determining their provision with natural history cabinets and botanical gardens. These included a wide variety of objects: naturalized specimens; zoological, anatomical and botanical models; osteological collections; herbaria; geological, mineralogical and fossil collections; crystallographic models and wall charts as well as instruments such as microscopes and projection apparatus. Inventories dating from 1928 from more than 80% of Portuguese secondary schools were analysed with the aim of understanding the economic and material conditions behind constitution and uses of collections, as well as pedagogical tendencies and teaching practices. Results will be presented, including differences and similarities between schools. Moreover, data from inventories were cross-checked with legislation, governmental directives and curricula in order to determine the extent of their actual implementation. The study of these inventories is crucial to understand the role of natural history collections both in the history of education and the history of science, as well as their role today.