At Subordinate clauses developed and reduced they are present in all subordinates, whether they are nouns, adjectives or adverbials. Thus, in view of this aspect, see each one of them, in order to expand your knowledge regarding the characteristics that demarcate them:
The teacher said she needed help.
We have two clauses: one constituted by the main clause (the teacher said) and the other that is defined by the subordinate clause direct objective substantive (which needed help).
In view of these assumptions, as there is the presence of the integral conjunction, we affirm that it is a Subordinate substantive clause developed.
Let's look at it another way:
The teacher stated to need of help.
We now have a subordinate clause direct objective noun reduced from infinitive (because the verb is expressed in such a form).
We looked at the students who played in the school yard.
We infer that this is a restrictive adjectival subordinate clause, by the fact that the relative pronoun “that” (which can be replaced by the pronoun “which”) is present in the clause.
Looking at it another way, we have:
We looked at the students playing in the yard.
We now have a reduced restrictive adjective subordinate clause of a gerund.
as soon as i entered school I knew what had happened.
The highlighted clause is classified as a temporal adverbial subordinate clause.
Analyzing it in another way, we have:
entering school I knew what had happened.
Now we are faced with an adverbial subordinate clause reduced to a gerund.
By Vânia Duarte
Graduated in Letters
Source: Brazil School - https://brasilescola.uol.com.br/gramatica/oracoes-subordinadas-desenvolvidas-reduzidas.htm