Resolved
A new tag precalculus was created. It should probably be synonym of algebra-precalculus.
AFAIK precalculus is American term. That's why I asked in chat for some feedback from people familiar with American education system. The feedback was that they should be synonyms. (If the new tag is needed at all.) But of course, if there are any reasons why this would not be a correct action, we can discuss it in comment to this post.
EDIT: I have just noticed that this synonym has already been suggestedhas already been suggested. Users with score at leat 5 on the algebra-precalculus can vote for (or against) this synonym.