Scratch-www: Use less US-centric names in teacher registration

[chrisgarrity]

High school and middle school are both very US-centric names for schools, and don't necessarily have an equivalent in other countries. Both are considered 'secondary school' in many places. We may want to consider changing the text to make it easier to localize.

[TheGrits]

@chrisgarrity I can confirm that this is the case here in Canada. High school and secondary school are interchangeable terms here, but university/college is usually called postsecondary education.

[rschamp]

Maybe we should set these to child age ranges rather than terms for the schooling?

[christan1029]

How about keeping the terms of the schooling, but also including the age ranges in parentheses?

Something like this-