SQLite3 Activerecord too slow

I've been using the activerecord adapter for sqlite (without rails), and when I try to insert anything it seems to be too slow. For instance when I do ~250 inserts it could easily take more than 5 minutes! My schema is the following:

create_table :courses do |t|
    t.string :title
    t.integer :ethmmy_id
end

add_index :courses, :ethmmy_id

create_table :announcements do |t|
    t.string :title
    t.string :author
    t.string :body
    t.string :uhash
    t.belongs_to :courses
    t.timestamps null: false
end

add_index :announcements, :courses_id

The ActiveRecord models I use are the following:

class Course < ActiveRecord::Base
    validates :ethmmy_id, uniqueness: true
    has_many :announcements
end

class Announcement < ActiveRecord::Base
    validates :uhash, uniqueness: true
    belongs_to :course
end

I've tried modifying the PRAGMAS like setting the journal in memory or setting synchronous I/O off but there doesn't seem to be much of a difference. The data is fetched from a web crawler but that is not the bottleneck, as the crawler is pretty fast by itself.