Were children taught English as a language or any other languages? Or did they only learn German? To be specific, schoolchildren aged 12 or above.
As a couple of comments have already indicated, English was taught at school in Germany while the Nazis were in power. English replaced French as the main foreign language taught:
a hierarchy of European foreign languages was set up in which preference was given to Germanic over Romanic and Slavic languages. This meant that French lost its status as a second language in Germany which, traditionally, had been very high. English became by far the most prominent foreign language in Germany because Nazi ideology saw the English and their language as akin to the "Aryan race"
Source: Jan Hollm, Foreign Language Teaching under National Socialism (2004)
This change did not happen immediately though as the Nazis had no clear plan for education before they came to power. There were some differences between what boys and girls were offered, and differences also existed between different kinds of schools.
In secondary schools English became the regular first foreign language at school. For boys Latin became the second foreign language. In schools that concentrated on the instruction of modern foreign languages rather than on sciences French, Italian or Spanish were offered as a voluntary third foreign language. Girls could choose between French or Latin as a second foreign language. If a sufficient number of secondary schools existed, some traditional grammar schools were kept where pupils started with Latin as a first foreign language, followed by classical Greek and English. So-called middle schools that did not prepare pupils for higher education but for learning a trade also offered English as the first and usually only foreign language. Through these changes French became marginalized and English became the most important foreign language in German schools.
The reasons for the marginalization of French were
of a racist nature. According to Nazi ideology the French derived from the Germanic tribe of the Frankonians, but they had supposedly lost most of their Aryan blood due to intermarriage with people of other races. Furthermore, a severe loss of “Frankonian blood” had taken place in history because in wars the fearless, heroic Frankonian warriors had had to pay the highest toll in blood whereas the other ethnic groups, being cowardly, had tried to evade participating in fights.
There was even a handbook issued listing the reasons for "the racial decline of French". The relative importance given to Latin, on the other hand, stemmed from a
reverence for the Roman Empire as a demonstration of a Nietzschean "will to power" and the appreciation of the Romans as an Aryan people
This BBC page A Child's Memory of WW2 in Germany mentions an English teacher the author had:
My English teacher had taught German in a Stoke on Trent school and returned with addresses of the girls in England and suddenly I had a pen friend.
Of course, they did. See http://www.rsoelde.de/ARCHIV/05-1004.htm on the bottom of the linked page you can see a certificate which has "Englisch".