I am no expert, and I was not a student in the seventies, but I do remember some of the political upheavals, social and cultural currents and events.
Design is informed, develop in tandem with, or as a reaction against, politics and the happenings in society in general.
Yes, there was definitely a good deal of sixties hippy aesthetics around in the seventies; it had by that time become more accepted and more mainstream. The psychedelic elements not so "dangerous" and subversive anymore, the "peace and love" of civil disobedience and non-violent protest, with their organic flower-multicoloured aesthetics would "have to go": inevitable the political pendulum swings.
There was experimenting with printing techniques in the sixties, and you will find the madness of pouring several colours into the same colour well in offset printing presses. The eventual result is that the whole thing turns brownish, but you can print a good deal before the colours mix, and you will get a bunch of posters that are all slightly different. I.e.: there would be no raster. I can find no example, but imagine that you put several colour in this:
Edit: I found the picture I was looking for:
Sixties. Would you buy this lipstick?
Though made in 1967, Milton Glasers Bob Dylan album design shows a tight visual language. My point is that the "hippy-like" hair is not in wild hippy colours. They are muted. The font and silhouette speaks of a minimalist contrast.
There is a large difference between what you might call corporate design and undercurrents rooted in some kind of bottom-up visual languages. If you search for "1970 design" you will get a lot of - what was seen by many as - high-brow visual effects, designs for companies and new, wonderful technology. There are still a good deal of colours but not much of the organic flowery-thing. It is moving towards more simple, graphic elements. Compare business design with LP covers, concert posters, "grassroot" cultural events etc., there is a large gap.
Seventies. Would you buy this?
And of course, there is the controversial art of Andy Warhol, who "shamelessly" commercialised art. I guess you could call him the master of flat design :D.
Here, Liza Minelli:
The 1968 social unrest and conflict was a violent reaction to what was seen as military, capitalist, and bureaucratic elites. Many governments answered with an escalation of political repression and physical violence. Peaceful protest did not go anywhere. Man in the street, anti-establishment. Cold war, real war, revolutions, the fall of the British empire, Mao died. The world was big, cold, dangerous and confusing. Robots, science fiction, space exploration, star wars, dystopias, genetic manipulation; the world was becoming alien. The hope that the world could be better than it was, faltered.
Anyone could create anything. Anyone could create music. The technology then was making it easier for more people to dabble in art, music, design. The classic example of this is of course Sex Pistols. It was messy, it was do-it-yourself, it was loud (in all senses of the word). They took revered symbols and dissected them: the queen, the flag, religion, politicians. The grid was truly out the window, rules and consistency were for sissies. If you were tone-deaf, that would be a plus as a singer. The Clash was criticised as being too "melodic", not "genuine" punk. Upper class.
And here a play on Andy Warhols portrait of Marilyn Monroe:
The feminism movement in the 70ties took elements from punk; it was the visual language of protest. It was focused around the female body, the right to sexual freedom, equal pay and solidarity with women all around the globe.
Solidarity with Vietnamese women during the Vietnam war:
Being a student in the 1970ties, I would think there would be a pretty large gap and trench-war between the punk and "good taste." The post-modernist (term I despise) and analytical deconstruction clashed with "street" aesthetics. Other elements would be the "machine" aesthetics, the graphic art and music from David Bowie and Pink Floyd would be examples. Guess you could call it machine surrealism (as opposed to hippy organic surrealism), human-machine and the reinvention of our identity to what we are and what we create (i.e. technology).
It is worth noting that the punk movement was of course opposed to commercialism. As those that are part of punk grow older and we can sell them things, "their" language gets taken up by more mainstream commercialism, albeit in a milder version. Which is the case in many instances.
Not sure if I actually answered your question, but it was an attempt to put it into a historical context.
(next up would be the eighties and the crazy economic boom. But enough now.)